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third-party-mirror/openjdk/jdk25u/refs/heads/master/./src/hotspot/share/opto/loopTransform.cpp
blob: 58105afd9d54a67408b3b8aea0fcdda81b07f472 [file] [edit]
/*
* Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "compiler/compileLog.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/c2/barrierSetC2.hpp"
#include "memory/allocation.inline.hpp"
#include "opto/addnode.hpp"
#include "opto/callnode.hpp"
#include "opto/castnode.hpp"
#include "opto/connode.hpp"
#include "opto/convertnode.hpp"
#include "opto/divnode.hpp"
#include "opto/loopnode.hpp"
#include "opto/mulnode.hpp"
#include "opto/movenode.hpp"
#include "opto/opaquenode.hpp"
#include "opto/phase.hpp"
#include "opto/predicates.hpp"
#include "opto/rootnode.hpp"
#include "opto/runtime.hpp"
#include "opto/subnode.hpp"
#include "opto/superword.hpp"
#include "opto/vectornode.hpp"
#include "runtime/globals_extension.hpp"
#include "runtime/stubRoutines.hpp"
//------------------------------is_loop_exit-----------------------------------
// Given an IfNode, return the loop-exiting projection or null if both
// arms remain in the loop.
Node *IdealLoopTree::is_loop_exit(Node *iff) const {
if (iff->outcnt() != 2) return nullptr; // Ignore partially dead tests
PhaseIdealLoop *phase = _phase;
// Test is an IfNode, has 2 projections. If BOTH are in the loop
// we need loop unswitching instead of peeling.
if (!is_member(phase->get_loop(iff->raw_out(0))))
return iff->raw_out(0);
if (!is_member(phase->get_loop(iff->raw_out(1))))
return iff->raw_out(1);
return nullptr;
}
//=============================================================================
//------------------------------record_for_igvn----------------------------
// Put loop body on igvn work list
void IdealLoopTree::record_for_igvn() {
for (uint i = 0; i < _body.size(); i++) {
Node *n = _body.at(i);
_phase->_igvn._worklist.push(n);
}
// put body of outer strip mined loop on igvn work list as well
if (_head->is_CountedLoop() && _head->as_Loop()->is_strip_mined()) {
CountedLoopNode* l = _head->as_CountedLoop();
Node* outer_loop = l->outer_loop();
assert(outer_loop != nullptr, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop);
Node* outer_loop_tail = l->outer_loop_tail();
assert(outer_loop_tail != nullptr, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop_tail);
Node* outer_loop_end = l->outer_loop_end();
assert(outer_loop_end != nullptr, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop_end);
Node* outer_safepoint = l->outer_safepoint();
assert(outer_safepoint != nullptr, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_safepoint);
Node* cle_out = _head->as_CountedLoop()->loopexit()->proj_out(false);
assert(cle_out != nullptr, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(cle_out);
}
}
//------------------------------compute_exact_trip_count-----------------------
// Compute loop trip count if possible. Do not recalculate trip count for
// split loops (pre-main-post) which have their limits and inits behind Opaque node.
void IdealLoopTree::compute_trip_count(PhaseIdealLoop* phase) {
if (!_head->as_Loop()->is_valid_counted_loop(T_INT)) {
return;
}
CountedLoopNode* cl = _head->as_CountedLoop();
// Trip count may become nonexact for iteration split loops since
// RCE modifies limits. Note, _trip_count value is not reset since
// it is used to limit unrolling of main loop.
cl->set_nonexact_trip_count();
// Loop's test should be part of loop.
if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
return; // Infinite loop
#ifdef ASSERT
BoolTest::mask bt = cl->loopexit()->test_trip();
assert(bt == BoolTest::lt || bt == BoolTest::gt ||
bt == BoolTest::ne, "canonical test is expected");
#endif
Node* init_n = cl->init_trip();
Node* limit_n = cl->limit();
if (init_n != nullptr && limit_n != nullptr) {
// Use longs to avoid integer overflow.
int stride_con = cl->stride_con();
const TypeInt* init_type = phase->_igvn.type(init_n)->is_int();
const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
jlong init_con = (stride_con > 0) ? init_type->_lo : init_type->_hi;
jlong limit_con = (stride_con > 0) ? limit_type->_hi : limit_type->_lo;
int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
// The loop body is always executed at least once even if init >= limit (for stride_con > 0) or
// init <= limit (for stride_con < 0).
trip_count = MAX2(trip_count, (jlong)1);
if (trip_count < (jlong)max_juint) {
if (init_n->is_Con() && limit_n->is_Con()) {
// Set exact trip count.
cl->set_exact_trip_count((uint)trip_count);
} else if (cl->unrolled_count() == 1) {
// Set maximum trip count before unrolling.
cl->set_trip_count((uint)trip_count);
}
}
}
}
//------------------------------compute_profile_trip_cnt----------------------------
// Compute loop trip count from profile data as
// (backedge_count + loop_exit_count) / loop_exit_count
float IdealLoopTree::compute_profile_trip_cnt_helper(Node* n) {
if (n->is_If()) {
IfNode *iff = n->as_If();
if (iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN) {
Node *exit = is_loop_exit(iff);
if (exit) {
float exit_prob = iff->_prob;
if (exit->Opcode() == Op_IfFalse) {
exit_prob = 1.0 - exit_prob;
}
if (exit_prob > PROB_MIN) {
float exit_cnt = iff->_fcnt * exit_prob;
return exit_cnt;
}
}
}
}
if (n->is_Jump()) {
JumpNode *jmp = n->as_Jump();
if (jmp->_fcnt != COUNT_UNKNOWN) {
float* probs = jmp->_probs;
float exit_prob = 0;
PhaseIdealLoop *phase = _phase;
for (DUIterator_Fast imax, i = jmp->fast_outs(imax); i < imax; i++) {
JumpProjNode* u = jmp->fast_out(i)->as_JumpProj();
if (!is_member(_phase->get_loop(u))) {
exit_prob += probs[u->_con];
}
}
return exit_prob * jmp->_fcnt;
}
}
return 0;
}
void IdealLoopTree::compute_profile_trip_cnt(PhaseIdealLoop *phase) {
if (!_head->is_Loop()) {
return;
}
LoopNode* head = _head->as_Loop();
if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
return; // Already computed
}
float trip_cnt = (float)max_jint; // default is big
Node* back = head->in(LoopNode::LoopBackControl);
while (back != head) {
if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
back->in(0) &&
back->in(0)->is_If() &&
back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
back->in(0)->as_If()->_prob != PROB_UNKNOWN &&
(back->Opcode() == Op_IfTrue ? 1-back->in(0)->as_If()->_prob : back->in(0)->as_If()->_prob) > PROB_MIN) {
break;
}
back = phase->idom(back);
}
if (back != head) {
assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
back->in(0), "if-projection exists");
IfNode* back_if = back->in(0)->as_If();
float loop_back_cnt = back_if->_fcnt * (back->Opcode() == Op_IfTrue ? back_if->_prob : (1 - back_if->_prob));
// Now compute a loop exit count
float loop_exit_cnt = 0.0f;
if (_child == nullptr) {
for (uint i = 0; i < _body.size(); i++) {
Node *n = _body[i];
loop_exit_cnt += compute_profile_trip_cnt_helper(n);
}
} else {
ResourceMark rm;
Unique_Node_List wq;
wq.push(back);
for (uint i = 0; i < wq.size(); i++) {
Node *n = wq.at(i);
assert(n->is_CFG(), "only control nodes");
if (n != head) {
if (n->is_Region()) {
for (uint j = 1; j < n->req(); j++) {
wq.push(n->in(j));
}
} else {
loop_exit_cnt += compute_profile_trip_cnt_helper(n);
wq.push(n->in(0));
}
}
}
}
if (loop_exit_cnt > 0.0f) {
trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
} else {
// No exit count so use
trip_cnt = loop_back_cnt;
}
} else {
head->mark_profile_trip_failed();
}
#ifndef PRODUCT
if (TraceProfileTripCount) {
tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
}
#endif
head->set_profile_trip_cnt(trip_cnt);
}
// Return nonzero index of invariant operand for an associative
// binary operation of (nonconstant) invariant and variant values.
// Helper for reassociate_invariants.
int IdealLoopTree::find_invariant(Node* n, PhaseIdealLoop* phase) {
bool in1_invar = this->is_invariant(n->in(1));
bool in2_invar = this->is_invariant(n->in(2));
if (in1_invar && !in2_invar) return 1;
if (!in1_invar && in2_invar) return 2;
return 0;
}
// Return TRUE if "n" is an associative cmp node. A cmp node is
// associative if it is only used for equals or not-equals
// comparisons of integers or longs. We cannot reassociate
// non-equality comparisons due to possibility of overflow.
bool IdealLoopTree::is_associative_cmp(Node* n) {
if (n->Opcode() != Op_CmpI && n->Opcode() != Op_CmpL) {
return false;
}
for (DUIterator i = n->outs(); n->has_out(i); i++) {
BoolNode* bool_out = n->out(i)->isa_Bool();
if (bool_out == nullptr || !(bool_out->_test._test == BoolTest::eq ||
bool_out->_test._test == BoolTest::ne)) {
return false;
}
}
return true;
}
// Return TRUE if "n" is an associative binary node. If "base" is
// not null, "n" must be re-associative with it.
bool IdealLoopTree::is_associative(Node* n, Node* base) {
int op = n->Opcode();
if (base != nullptr) {
assert(is_associative(base), "Base node should be associative");
int base_op = base->Opcode();
if (base_op == Op_AddI || base_op == Op_SubI || base_op == Op_CmpI) {
return op == Op_AddI || op == Op_SubI;
}
if (base_op == Op_AddL || base_op == Op_SubL || base_op == Op_CmpL) {
return op == Op_AddL || op == Op_SubL;
}
return op == base_op;
} else {
// Integer "add/sub/mul/and/or/xor" operations are associative. Integer
// "cmp" operations are associative if it is an equality comparison.
return op == Op_AddI || op == Op_AddL
|| op == Op_SubI || op == Op_SubL
|| op == Op_MulI || op == Op_MulL
|| op == Op_AndI || op == Op_AndL
|| op == Op_OrI || op == Op_OrL
|| op == Op_XorI || op == Op_XorL
|| is_associative_cmp(n);
}
}
// Reassociate invariant add and subtract expressions:
//
// inv1 + (x + inv2) => ( inv1 + inv2) + x
// (x + inv2) + inv1 => ( inv1 + inv2) + x
// inv1 + (x - inv2) => ( inv1 - inv2) + x
// inv1 - (inv2 - x) => ( inv1 - inv2) + x
// (x + inv2) - inv1 => (-inv1 + inv2) + x
// (x - inv2) + inv1 => ( inv1 - inv2) + x
// (x - inv2) - inv1 => (-inv1 - inv2) + x
// inv1 + (inv2 - x) => ( inv1 + inv2) - x
// inv1 - (x - inv2) => ( inv1 + inv2) - x
// (inv2 - x) + inv1 => ( inv1 + inv2) - x
// (inv2 - x) - inv1 => (-inv1 + inv2) - x
// inv1 - (x + inv2) => ( inv1 - inv2) - x
//
// Apply the same transformations to == and !=
// inv1 == (x + inv2) => ( inv1 - inv2 ) == x
// inv1 == (x - inv2) => ( inv1 + inv2 ) == x
// inv1 == (inv2 - x) => (-inv1 + inv2 ) == x
Node* IdealLoopTree::reassociate_add_sub_cmp(Node* n1, int inv1_idx, int inv2_idx, PhaseIdealLoop* phase) {
Node* n2 = n1->in(3 - inv1_idx);
bool n1_is_sub = n1->is_Sub() && !n1->is_Cmp();
bool n1_is_cmp = n1->is_Cmp();
bool n2_is_sub = n2->is_Sub();
assert(n1->is_Add() || n1_is_sub || n1_is_cmp, "Target node should be add, subtract, or compare");
assert(n2->is_Add() || (n2_is_sub && !n2->is_Cmp()), "Child node should be add or subtract");
Node* inv1 = n1->in(inv1_idx);
Node* inv2 = n2->in(inv2_idx);
Node* x = n2->in(3 - inv2_idx);
// Determine whether x, inv1, or inv2 should be negative in the transformed
// expression
bool neg_x = n2_is_sub && inv2_idx == 1;
bool neg_inv2 = (n2_is_sub && !n1_is_cmp && inv2_idx == 2) || (n1_is_cmp && !n2_is_sub);
bool neg_inv1 = (n1_is_sub && inv1_idx == 2) || (n1_is_cmp && inv2_idx == 1 && n2_is_sub);
if (n1_is_sub && inv1_idx == 1) {
neg_x = !neg_x;
neg_inv2 = !neg_inv2;
}
bool is_int = n2->bottom_type()->isa_int() != nullptr;
Node* inv1_c = phase->get_ctrl(inv1);
Node* n_inv1;
if (neg_inv1) {
if (is_int) {
n_inv1 = new SubINode(phase->intcon(0), inv1);
} else {
n_inv1 = new SubLNode(phase->longcon(0L), inv1);
}
phase->register_new_node(n_inv1, inv1_c);
} else {
n_inv1 = inv1;
}
Node* inv;
if (is_int) {
if (neg_inv2) {
inv = new SubINode(n_inv1, inv2);
} else {
inv = new AddINode(n_inv1, inv2);
}
phase->register_new_node(inv, phase->get_early_ctrl(inv));
if (n1_is_cmp) {
return new CmpINode(x, inv);
}
if (neg_x) {
return new SubINode(inv, x);
} else {
return new AddINode(x, inv);
}
} else {
if (neg_inv2) {
inv = new SubLNode(n_inv1, inv2);
} else {
inv = new AddLNode(n_inv1, inv2);
}
phase->register_new_node(inv, phase->get_early_ctrl(inv));
if (n1_is_cmp) {
return new CmpLNode(x, inv);
}
if (neg_x) {
return new SubLNode(inv, x);
} else {
return new AddLNode(x, inv);
}
}
}
// Reassociate invariant binary expressions with add/sub/mul/
// and/or/xor/cmp operators.
// For add/sub/cmp expressions: see "reassociate_add_sub_cmp"
//
// For mul/and/or/xor expressions:
//
// inv1 op (x op inv2) => (inv1 op inv2) op x
//
Node* IdealLoopTree::reassociate(Node* n1, PhaseIdealLoop *phase) {
if (!is_associative(n1) || n1->outcnt() == 0) return nullptr;
if (is_invariant(n1)) return nullptr;
// Don't mess with add of constant (igvn moves them to expression tree root.)
if (n1->is_Add() && n1->in(2)->is_Con()) return nullptr;
int inv1_idx = find_invariant(n1, phase);
if (!inv1_idx) return nullptr;
Node* n2 = n1->in(3 - inv1_idx);
if (!is_associative(n2, n1)) return nullptr;
int inv2_idx = find_invariant(n2, phase);
if (!inv2_idx) return nullptr;
if (!phase->may_require_nodes(10, 10)) return nullptr;
Node* result = nullptr;
switch (n1->Opcode()) {
case Op_AddI:
case Op_AddL:
case Op_SubI:
case Op_SubL:
case Op_CmpI:
case Op_CmpL:
result = reassociate_add_sub_cmp(n1, inv1_idx, inv2_idx, phase);
break;
case Op_MulI:
case Op_MulL:
case Op_AndI:
case Op_AndL:
case Op_OrI:
case Op_OrL:
case Op_XorI:
case Op_XorL: {
Node* inv1 = n1->in(inv1_idx);
Node* inv2 = n2->in(inv2_idx);
Node* x = n2->in(3 - inv2_idx);
Node* inv = n2->clone_with_data_edge(inv1, inv2);
phase->register_new_node(inv, phase->get_early_ctrl(inv));
result = n1->clone_with_data_edge(x, inv);
break;
}
default:
ShouldNotReachHere();
}
assert(result != nullptr, "");
phase->register_new_node_with_ctrl_of(result, n1);
phase->_igvn.replace_node(n1, result);
assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
_body.yank(n1);
return result;
}
//---------------------reassociate_invariants-----------------------------
// Reassociate invariant expressions:
void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
for (int i = _body.size() - 1; i >= 0; i--) {
Node *n = _body.at(i);
for (int j = 0; j < 5; j++) {
Node* nn = reassociate(n, phase);
if (nn == nullptr) break;
n = nn; // again
}
}
}
//------------------------------policy_peeling---------------------------------
// Return TRUE if the loop should be peeled, otherwise return FALSE. Peeling
// is applicable if we can make a loop-invariant test (usually a null-check)
// execute before we enter the loop. When TRUE, the estimated node budget is
// also requested.
bool IdealLoopTree::policy_peeling(PhaseIdealLoop *phase) {
uint estimate = estimate_peeling(phase);
return estimate == 0 ? false : phase->may_require_nodes(estimate);
}
// Perform actual policy and size estimate for the loop peeling transform, and
// return the estimated loop size if peeling is applicable, otherwise return
// zero. No node budget is allocated.
uint IdealLoopTree::estimate_peeling(PhaseIdealLoop *phase) {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Peeling does loop cloning which can result in O(N^2) node construction.
if (_body.size() > 255 && !StressLoopPeeling) {
return 0; // Suppress too large body size.
}
// Optimistic estimate that approximates loop body complexity via data and
// control flow fan-out (instead of using the more pessimistic: BodySize^2).
uint estimate = est_loop_clone_sz(2);
if (phase->exceeding_node_budget(estimate)) {
return 0; // Too large to safely clone.
}
// Check for vectorized loops, any peeling done was already applied.
if (_head->is_CountedLoop()) {
CountedLoopNode* cl = _head->as_CountedLoop();
if (cl->is_unroll_only() || cl->trip_count() == 1) {
// Peeling is not legal here (cf. assert in do_peeling), we don't even stress peel!
return 0;
}
}
#ifndef PRODUCT
// It is now safe to peel or not.
if (StressLoopPeeling) {
LoopNode* loop_head = _head->as_Loop();
static constexpr uint max_peeling_opportunities = 5;
if (loop_head->_stress_peeling_attempts < max_peeling_opportunities) {
loop_head->_stress_peeling_attempts++;
// In case of stress, let's just pick randomly...
return ((phase->C->random() % 2) == 0) ? estimate : 0;
}
return 0;
}
// ...otherwise, let's apply our heuristic.
#endif
Node* test = tail();
while (test != _head) { // Scan till run off top of loop
if (test->is_If()) { // Test?
Node *ctrl = phase->get_ctrl(test->in(1));
if (ctrl->is_top()) {
return 0; // Found dead test on live IF? No peeling!
}
// Standard IF only has one input value to check for loop invariance.
assert(test->Opcode() == Op_If ||
test->Opcode() == Op_CountedLoopEnd ||
test->Opcode() == Op_LongCountedLoopEnd ||
test->Opcode() == Op_RangeCheck ||
test->Opcode() == Op_ParsePredicate,
"Check this code when new subtype is added");
// Condition is not a member of this loop?
if (!is_member(phase->get_loop(ctrl)) && is_loop_exit(test)) {
return estimate; // Found reason to peel!
}
}
// Walk up dominators to loop _head looking for test which is executed on
// every path through the loop.
test = phase->idom(test);
}
return 0;
}
//------------------------------peeled_dom_test_elim---------------------------
// If we got the effect of peeling, either by actually peeling or by making
// a pre-loop which must execute at least once, we can remove all
// loop-invariant dominated tests in the main body.
void PhaseIdealLoop::peeled_dom_test_elim(IdealLoopTree* loop, Node_List& old_new) {
bool progress = true;
while (progress) {
progress = false; // Reset for next iteration
Node* prev = loop->_head->in(LoopNode::LoopBackControl); // loop->tail();
Node* test = prev->in(0);
while (test != loop->_head) { // Scan till run off top of loop
int p_op = prev->Opcode();
assert(test != nullptr, "test cannot be null");
Node* test_cond = nullptr;
if ((p_op == Op_IfFalse || p_op == Op_IfTrue) && test->is_If()) {
test_cond = test->in(1);
}
if (test_cond != nullptr && // Test?
!test_cond->is_Con() && // And not already obvious?
// And condition is not a member of this loop?
!loop->is_member(get_loop(get_ctrl(test_cond)))) {
// Walk loop body looking for instances of this test
for (uint i = 0; i < loop->_body.size(); i++) {
Node* n = loop->_body.at(i);
// Check against cached test condition because dominated_by()
// replaces the test condition with a constant.
if (n->is_If() && n->in(1) == test_cond) {
// IfNode was dominated by version in peeled loop body
progress = true;
dominated_by(old_new[prev->_idx]->as_IfProj(), n->as_If());
}
}
}
prev = test;
test = idom(test);
} // End of scan tests in loop
} // End of while (progress)
}
//------------------------------do_peeling-------------------------------------
// Peel the first iteration of the given loop.
// Step 1: Clone the loop body. The clone becomes the peeled iteration.
// The pre-loop illegally has 2 control users (old & new loops).
// Step 2: Make the old-loop fall-in edges point to the peeled iteration.
// Do this by making the old-loop fall-in edges act as if they came
// around the loopback from the prior iteration (follow the old-loop
// backedges) and then map to the new peeled iteration. This leaves
// the pre-loop with only 1 user (the new peeled iteration), but the
// peeled-loop backedge has 2 users.
// Step 3: Cut the backedge on the clone (so its not a loop) and remove the
// extra backedge user.
//
// orig
//
// stmt1
// |
// v
// predicates
// |
// v
// loop<----+
// | |
// stmt2 |
// | |
// v |
// if ^
// / \ |
// / \ |
// v v |
// false true |
// / \ |
// / ----+
// |
// v
// exit
//
//
// after clone loop
//
// stmt1
// |
// v
// predicates
// / \
// clone / \ orig
// / \
// / \
// v v
// +---->loop clone loop<----+
// | | | |
// | stmt2 clone stmt2 |
// | | | |
// | v v |
// ^ if clone If ^
// | / \ / \ |
// | / \ / \ |
// | v v v v |
// | true false false true |
// | / \ / \ |
// +---- \ / ----+
// \ /
// 1v v2
// region
// |
// v
// exit
//
//
// after peel and predicate move
//
// stmt1
// |
// v
// predicates
// /
// /
// clone / orig
// /
// / +----------+
// / | |
// / | |
// / | |
// v v |
// TOP-->loop clone loop<----+ |
// | | | |
// stmt2 clone stmt2 | |
// | | | ^
// v v | |
// if clone If ^ |
// / \ / \ | |
// / \ / \ | |
// v v v v | |
// true false false true | |
// | \ / \ | |
// | \ / ----+ ^
// | \ / |
// | 1v v2 |
// v region |
// | | |
// | v |
// | exit |
// | |
// +--------------->-----------------+
//
//
// final graph
//
// stmt1
// |
// v
// predicates
// |
// v
// stmt2 clone
// |
// v
// if clone
// / |
// / |
// v v
// false true
// | |
// | v
// | Initialized Assertion Predicates
// | |
// | v
// | loop<----+
// | | |
// | stmt2 |
// | | |
// | v |
// v if ^
// | / \ |
// | / \ |
// | v v |
// | false true |
// | | \ |
// v v --+
// region
// |
// v
// exit
//
void PhaseIdealLoop::do_peeling(IdealLoopTree *loop, Node_List &old_new) {
C->set_major_progress();
// Peeling a 'main' loop in a pre/main/post situation obfuscates the
// 'pre' loop from the main and the 'pre' can no longer have its
// iterations adjusted. Therefore, we need to declare this loop as
// no longer a 'main' loop; it will need new pre and post loops before
// we can do further RCE.
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Peel ");
loop->dump_head();
}
#endif
LoopNode* head = loop->_head->as_Loop();
C->print_method(PHASE_BEFORE_LOOP_PEELING, 4, head);
bool counted_loop = head->is_CountedLoop();
if (counted_loop) {
CountedLoopNode *cl = head->as_CountedLoop();
assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
cl->set_trip_count(cl->trip_count() - 1);
if (cl->is_main_loop()) {
cl->set_normal_loop();
if (cl->is_multiversion()) {
// Peeling also destroys the connection of the main loop
// to the multiversion_if.
cl->set_no_multiversion();
}
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Peeling a 'main' loop; resetting to 'normal' ");
}
#endif
}
}
// Step 1: Clone the loop body. The clone becomes the peeled iteration.
// The pre-loop illegally has 2 control users (old & new loops).
const uint first_node_index_in_post_loop_body = Compile::current()->unique();
LoopNode* outer_loop_head = head->skip_strip_mined();
clone_loop(loop, old_new, dom_depth(outer_loop_head), ControlAroundStripMined);
// Step 2: Make the old-loop fall-in edges point to the peeled iteration.
// Do this by making the old-loop fall-in edges act as if they came
// around the loopback from the prior iteration (follow the old-loop
// backedges) and then map to the new peeled iteration. This leaves
// the pre-loop with only 1 user (the new peeled iteration), but the
// peeled-loop backedge has 2 users.
Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
_igvn.hash_delete(outer_loop_head);
outer_loop_head->set_req(LoopNode::EntryControl, new_entry);
for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
Node* old = head->fast_out(j);
if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
if (!new_exit_value) // Backedge value is ALSO loop invariant?
// Then loop body backedge value remains the same.
new_exit_value = old->in(LoopNode::LoopBackControl);
_igvn.hash_delete(old);
old->set_req(LoopNode::EntryControl, new_exit_value);
}
}
// Step 3: Cut the backedge on the clone (so its not a loop) and remove the
// extra backedge user.
Node* new_head = old_new[head->_idx];
_igvn.hash_delete(new_head);
new_head->set_req(LoopNode::LoopBackControl, C->top());
for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
Node* use = new_head->fast_out(j2);
if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
_igvn.hash_delete(use);
use->set_req(LoopNode::LoopBackControl, C->top());
}
}
// Step 4: Correct dom-depth info. Set to loop-head depth.
int dd_outer_loop_head = dom_depth(outer_loop_head);
set_idom(outer_loop_head, outer_loop_head->in(LoopNode::EntryControl), dd_outer_loop_head);
for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
Node *old = loop->_body.at(j3);
Node *nnn = old_new[old->_idx];
if (!has_ctrl(nnn)) {
set_idom(nnn, idom(nnn), dd_outer_loop_head-1);
}
}
// Step 5: Assertion Predicates initialization
if (counted_loop) {
CountedLoopNode* cl = head->as_CountedLoop();
Node* init = cl->init_trip();
Node* init_ctrl = cl->skip_strip_mined()->in(LoopNode::EntryControl);
initialize_assertion_predicates_for_peeled_loop(new_head->as_CountedLoop(), cl,
first_node_index_in_post_loop_body, old_new);
cast_incr_before_loop(init, init_ctrl, cl);
}
// Now force out all loop-invariant dominating tests. The optimizer
// finds some, but we _know_ they are all useless.
peeled_dom_test_elim(loop,old_new);
loop->record_for_igvn();
C->print_method(PHASE_AFTER_LOOP_PEELING, 4, new_head);
}
//------------------------------policy_maximally_unroll------------------------
// Calculate the exact loop trip-count and return TRUE if loop can be fully,
// i.e. maximally, unrolled, otherwise return FALSE. When TRUE, the estimated
// node budget is also requested.
bool IdealLoopTree::policy_maximally_unroll(PhaseIdealLoop* phase) const {
CountedLoopNode* cl = _head->as_CountedLoop();
assert(cl->is_normal_loop(), "");
if (!cl->is_valid_counted_loop(T_INT)) {
return false; // Malformed counted loop.
}
if (!cl->has_exact_trip_count()) {
return false; // Trip count is not exact.
}
uint trip_count = cl->trip_count();
// Note, max_juint is used to indicate unknown trip count.
assert(trip_count > 1, "one iteration loop should be optimized out already");
assert(trip_count < max_juint, "exact trip_count should be less than max_juint.");
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Allow the unrolled body to get larger than the standard loop size limit.
uint unroll_limit = (uint)LoopUnrollLimit * 4;
assert((intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
if (trip_count > unroll_limit || _body.size() > unroll_limit) {
return false;
}
uint new_body_size = est_loop_unroll_sz(trip_count);
if (new_body_size == UINT_MAX) { // Check for bad estimate (overflow).
return false;
}
// Fully unroll a loop with few iterations, regardless of other conditions,
// since the following (general) loop optimizations will split such loop in
// any case (into pre-main-post).
if (trip_count <= 3) {
return phase->may_require_nodes(new_body_size);
}
// Reject if unrolling will result in too much node construction.
if (new_body_size > unroll_limit || phase->exceeding_node_budget(new_body_size)) {
return false;
}
// Do not unroll a loop with String intrinsics code.
// String intrinsics are large and have loops.
for (uint k = 0; k < _body.size(); k++) {
Node* n = _body.at(k);
switch (n->Opcode()) {
case Op_StrComp:
case Op_StrEquals:
case Op_VectorizedHashCode:
case Op_StrIndexOf:
case Op_StrIndexOfChar:
case Op_EncodeISOArray:
case Op_AryEq:
case Op_CountPositives: {
return false;
}
} // switch
}
return phase->may_require_nodes(new_body_size);
}
//------------------------------policy_unroll----------------------------------
// Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll if
// the loop is a counted loop and the loop body is small enough. When TRUE,
// the estimated node budget is also requested.
bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
CountedLoopNode *cl = _head->as_CountedLoop();
assert(cl->is_normal_loop() || cl->is_main_loop(), "");
if (!cl->is_valid_counted_loop(T_INT)) {
return false; // Malformed counted loop
}
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Protect against over-unrolling.
// After split at least one iteration will be executed in pre-loop.
if (cl->trip_count() <= (cl->is_normal_loop() ? 2u : 1u)) {
return false;
}
_local_loop_unroll_limit = LoopUnrollLimit;
_local_loop_unroll_factor = 4;
int future_unroll_cnt = cl->unrolled_count() * 2;
if (!cl->is_vectorized_loop()) {
if (future_unroll_cnt > LoopMaxUnroll) return false;
} else {
// obey user constraints on vector mapped loops with additional unrolling applied
int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1;
if ((future_unroll_cnt / unroll_constraint) > LoopMaxUnroll) return false;
}
const int stride_con = cl->stride_con();
// Check for initial stride being a small enough constant
const int initial_stride_sz = MAX2(1<<2, Matcher::max_vector_size(T_BYTE) / 2);
// Maximum stride size should protect against overflow, when doubling stride unroll_count times
const int max_stride_size = MIN2<int>(max_jint / 2 - 2, initial_stride_sz * future_unroll_cnt);
// No abs() use; abs(min_jint) = min_jint
if (stride_con < -max_stride_size || stride_con > max_stride_size) return false;
// Don't unroll if the next round of unrolling would push us
// over the expected trip count of the loop. One is subtracted
// from the expected trip count because the pre-loop normally
// executes 1 iteration.
if (UnrollLimitForProfileCheck > 0 &&
cl->profile_trip_cnt() != COUNT_UNKNOWN &&
future_unroll_cnt > UnrollLimitForProfileCheck &&
(float)future_unroll_cnt > cl->profile_trip_cnt() - 1.0) {
return false;
}
bool should_unroll = true;
// When unroll count is greater than LoopUnrollMin, don't unroll if:
// the residual iterations are more than 10% of the trip count
// and rounds of "unroll,optimize" are not making significant progress
// Progress defined as current size less than 20% larger than previous size.
if (phase->C->do_superword() &&
cl->node_count_before_unroll() > 0 &&
future_unroll_cnt > LoopUnrollMin &&
is_residual_iters_large(future_unroll_cnt, cl) &&
1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
if ((cl->slp_max_unroll() == 0) && !is_residual_iters_large(cl->unrolled_count(), cl)) {
// cl->slp_max_unroll() = 0 means that the previous slp analysis never passed.
// slp analysis may fail due to the loop IR is too complicated especially during the early stage
// of loop unrolling analysis. But after several rounds of loop unrolling and other optimizations,
// it's possible that the loop IR becomes simple enough to pass the slp analysis.
// So we don't return immediately in hoping that the next slp analysis can succeed.
should_unroll = false;
future_unroll_cnt = cl->unrolled_count();
} else {
return false;
}
}
Node *init_n = cl->init_trip();
Node *limit_n = cl->limit();
if (limit_n == nullptr) return false; // We will dereference it below.
// Non-constant bounds.
// Protect against over-unrolling when init or/and limit are not constant
// (so that trip_count's init value is maxint) but iv range is known.
if (init_n == nullptr || !init_n->is_Con() || !limit_n->is_Con()) {
Node* phi = cl->phi();
if (phi != nullptr) {
assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
int next_stride = stride_con * 2; // stride after this unroll
if (next_stride > 0) {
if (iv_type->_lo > max_jint - next_stride || // overflow
iv_type->_lo + next_stride > iv_type->_hi) {
return false; // over-unrolling
}
} else if (next_stride < 0) {
if (iv_type->_hi < min_jint - next_stride || // overflow
iv_type->_hi + next_stride < iv_type->_lo) {
return false; // over-unrolling
}
}
}
}
// After unroll limit will be adjusted: new_limit = limit-stride.
// Bailout if adjustment overflow.
const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
if ((stride_con > 0 && ((min_jint + stride_con) > limit_type->_hi)) ||
(stride_con < 0 && ((max_jint + stride_con) < limit_type->_lo)))
return false; // overflow
// Rudimentary cost model to estimate loop unrolling
// factor.
// Adjust body_size to determine if we unroll or not
uint body_size = _body.size();
// Key test to unroll loop in CRC32 java code
int xors_in_loop = 0;
// Also count ModL, DivL, MulL, and other nodes that expand mightly
for (uint k = 0; k < _body.size(); k++) {
Node* n = _body.at(k);
if (MemNode::barrier_data(n) != 0) {
body_size += BarrierSet::barrier_set()->barrier_set_c2()->estimated_barrier_size(n);
}
switch (n->Opcode()) {
case Op_XorI: xors_in_loop++; break; // CRC32 java code
case Op_ModL: body_size += 30; break;
case Op_DivL: body_size += 30; break;
case Op_MulL: body_size += 10; break;
case Op_RoundF:
case Op_RoundD: {
body_size += Matcher::scalar_op_pre_select_sz_estimate(n->Opcode(), n->bottom_type()->basic_type());
} break;
case Op_CountTrailingZerosV:
case Op_CountLeadingZerosV:
case Op_LoadVectorGather:
case Op_LoadVectorGatherMasked:
case Op_ReverseV:
case Op_RoundVF:
case Op_RoundVD:
case Op_VectorCastD2X:
case Op_VectorCastF2X:
case Op_PopCountVI:
case Op_PopCountVL: {
const TypeVect* vt = n->bottom_type()->is_vect();
body_size += Matcher::vector_op_pre_select_sz_estimate(n->Opcode(), vt->element_basic_type(), vt->length());
} break;
case Op_StrComp:
case Op_StrEquals:
case Op_StrIndexOf:
case Op_StrIndexOfChar:
case Op_EncodeISOArray:
case Op_AryEq:
case Op_VectorizedHashCode:
case Op_CountPositives: {
// Do not unroll a loop with String intrinsics code.
// String intrinsics are large and have loops.
return false;
}
} // switch
}
if (phase->C->do_superword()) {
// Only attempt slp analysis when user controls do not prohibit it
if (!range_checks_present() && (LoopMaxUnroll > _local_loop_unroll_factor)) {
// Once policy_slp_analysis succeeds, mark the loop with the
// maximal unroll factor so that we minimize analysis passes
if (future_unroll_cnt >= _local_loop_unroll_factor) {
policy_unroll_slp_analysis(cl, phase, future_unroll_cnt);
}
}
}
int slp_max_unroll_factor = cl->slp_max_unroll();
if ((LoopMaxUnroll < slp_max_unroll_factor) && FLAG_IS_DEFAULT(LoopMaxUnroll) && UseSubwordForMaxVector) {
LoopMaxUnroll = slp_max_unroll_factor;
}
uint estimate = est_loop_clone_sz(2);
if (cl->has_passed_slp()) {
if (slp_max_unroll_factor >= future_unroll_cnt) {
return should_unroll && phase->may_require_nodes(estimate);
}
return false; // Loop too big.
}
// Check for being too big
if (body_size > (uint)_local_loop_unroll_limit) {
if ((cl->is_subword_loop() || xors_in_loop >= 4) && body_size < 4u * LoopUnrollLimit) {
return should_unroll && phase->may_require_nodes(estimate);
}
return false; // Loop too big.
}
if (cl->is_unroll_only()) {
if (TraceSuperWordLoopUnrollAnalysis) {
tty->print_cr("policy_unroll passed vector loop(vlen=%d, factor=%d)\n",
slp_max_unroll_factor, future_unroll_cnt);
}
}
// Unroll once! (Each trip will soon do double iterations)
return should_unroll && phase->may_require_nodes(estimate);
}
void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_cnt) {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Enable this functionality target by target as needed
if (SuperWordLoopUnrollAnalysis) {
if (!cl->was_slp_analyzed()) {
Compile::TracePhase tp(Phase::_t_autoVectorize);
VLoop vloop(this, true);
if (vloop.check_preconditions()) {
SuperWord::unrolling_analysis(vloop, _local_loop_unroll_factor);
}
}
if (cl->has_passed_slp()) {
int slp_max_unroll_factor = cl->slp_max_unroll();
if (slp_max_unroll_factor >= future_unroll_cnt) {
int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor;
if (new_limit > LoopUnrollLimit) {
if (TraceSuperWordLoopUnrollAnalysis) {
tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit);
}
_local_loop_unroll_limit = new_limit;
}
}
}
}
}
//------------------------------policy_range_check-----------------------------
// Return TRUE or FALSE if the loop should be range-check-eliminated or not.
// When TRUE, the estimated node budget is also requested.
//
// We will actually perform iteration-splitting, a more powerful form of RCE.
bool IdealLoopTree::policy_range_check(PhaseIdealLoop* phase, bool provisional, BasicType bt) const {
if (!provisional && !RangeCheckElimination) return false;
// If nodes are depleted, some transform has miscalculated its needs.
assert(provisional || !phase->exceeding_node_budget(), "sanity");
if (_head->is_CountedLoop()) {
CountedLoopNode *cl = _head->as_CountedLoop();
// If we unrolled with no intention of doing RCE and we later changed our
// minds, we got no pre-loop. Either we need to make a new pre-loop, or we
// have to disallow RCE.
if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
// check for vectorized loops, some opts are no longer needed
// RCE needs pre/main/post loops. Don't apply it on a single iteration loop.
if (cl->is_unroll_only() || (cl->is_normal_loop() && cl->trip_count() == 1)) return false;
} else {
assert(provisional, "no long counted loop expected");
}
BaseCountedLoopNode* cl = _head->as_BaseCountedLoop();
Node *trip_counter = cl->phi();
assert(!cl->is_LongCountedLoop() || bt == T_LONG, "only long range checks in long counted loops");
assert(cl->is_valid_counted_loop(cl->bt()), "only for well formed loops");
// Check loop body for tests of trip-counter plus loop-invariant vs
// loop-invariant.
for (uint i = 0; i < _body.size(); i++) {
Node *iff = _body[i];
if (iff->Opcode() == Op_If ||
iff->Opcode() == Op_RangeCheck) { // Test?
// Comparing trip+off vs limit
Node* bol = iff->in(1);
if (bol->req() != 2) {
// Could be a dead constant test or another dead variant (e.g. a Phi with 2 inputs created with split_thru_phi).
// Either way, skip this test.
continue;
}
if (!bol->is_Bool()) {
assert(bol->is_OpaqueNotNull() ||
bol->is_OpaqueTemplateAssertionPredicate() ||
bol->is_OpaqueInitializedAssertionPredicate() ||
bol->is_OpaqueMultiversioning(),
"Opaque node of a non-null-check or an Assertion Predicate or Multiversioning");
continue;
}
if (bol->as_Bool()->_test._test == BoolTest::ne) {
continue; // not RC
}
Node *cmp = bol->in(1);
if (provisional) {
// Try to pattern match with either cmp inputs, do not check
// whether one of the inputs is loop independent as it may not
// have had a chance to be hoisted yet.
if (!phase->is_scaled_iv_plus_offset(cmp->in(1), trip_counter, bt, nullptr, nullptr) &&
!phase->is_scaled_iv_plus_offset(cmp->in(2), trip_counter, bt, nullptr, nullptr)) {
continue;
}
} else {
Node *rc_exp = cmp->in(1);
Node *limit = cmp->in(2);
Node *limit_c = phase->get_ctrl(limit);
if (limit_c == phase->C->top()) {
return false; // Found dead test on live IF? No RCE!
}
if (is_member(phase->get_loop(limit_c))) {
// Compare might have operands swapped; commute them
rc_exp = cmp->in(2);
limit = cmp->in(1);
limit_c = phase->get_ctrl(limit);
if (is_member(phase->get_loop(limit_c))) {
continue; // Both inputs are loop varying; cannot RCE
}
}
if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, bt, nullptr, nullptr)) {
continue;
}
}
// Found a test like 'trip+off vs limit'. Test is an IfNode, has two (2)
// projections. If BOTH are in the loop we need loop unswitching instead
// of iteration splitting.
if (is_loop_exit(iff)) {
// Found valid reason to split iterations (if there is room).
// NOTE: Usually a gross overestimate.
// Long range checks cause the loop to be transformed in a loop nest which only causes a fixed number of nodes
// to be added
return provisional || bt == T_LONG || phase->may_require_nodes(est_loop_clone_sz(2));
}
} // End of is IF
}
return false;
}
//------------------------------policy_peel_only-------------------------------
// Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
// for unrolling loops with NO array accesses.
bool IdealLoopTree::policy_peel_only(PhaseIdealLoop *phase) const {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// check for vectorized loops, any peeling done was already applied
if (_head->is_CountedLoop() && _head->as_CountedLoop()->is_unroll_only()) {
return false;
}
for (uint i = 0; i < _body.size(); i++) {
if (_body[i]->is_Mem()) {
return false;
}
}
// No memory accesses at all!
return true;
}
//------------------------------clone_up_backedge_goo--------------------------
// If Node n lives in the back_ctrl block and cannot float, we clone a private
// version of n in preheader_ctrl block and return that, otherwise return n.
Node *PhaseIdealLoop::clone_up_backedge_goo(Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones) {
if (get_ctrl(n) != back_ctrl) return n;
// Only visit once
if (visited.test_set(n->_idx)) {
Node *x = clones.find(n->_idx);
return (x != nullptr) ? x : n;
}
Node *x = nullptr; // If required, a clone of 'n'
// Check for 'n' being pinned in the backedge.
if (n->in(0) && n->in(0) == back_ctrl) {
assert(clones.find(n->_idx) == nullptr, "dead loop");
x = n->clone(); // Clone a copy of 'n' to preheader
clones.push(x, n->_idx);
x->set_req(0, preheader_ctrl); // Fix x's control input to preheader
}
// Recursive fixup any other input edges into x.
// If there are no changes we can just return 'n', otherwise
// we need to clone a private copy and change it.
for (uint i = 1; i < n->req(); i++) {
Node *g = clone_up_backedge_goo(back_ctrl, preheader_ctrl, n->in(i), visited, clones);
if (g != n->in(i)) {
if (!x) {
assert(clones.find(n->_idx) == nullptr, "dead loop");
x = n->clone();
clones.push(x, n->_idx);
}
x->set_req(i, g);
}
}
if (x) { // x can legally float to pre-header location
register_new_node(x, preheader_ctrl);
return x;
} else { // raise n to cover LCA of uses
set_ctrl(n, find_non_split_ctrl(back_ctrl->in(0)));
}
return n;
}
// When a counted loop is created, the loop phi type may be narrowed down. As a consequence, the control input of some
// nodes may be cleared: in particular in the case of a division by the loop iv, the Div node would lose its control
// dependency if the loop phi is never zero. After pre/main/post loops are created (and possibly unrolling), the
// loop phi type is only correct if the loop is indeed reachable: there's an implicit dependency between the loop phi
// type and the zero trip guard for the main or post loop and as a consequence a dependency between the Div node and the
// zero trip guard. This makes the dependency explicit by adding a CastII for the loop entry input of the loop phi. If
// the backedge of the main or post loop is removed, a Div node won't be able to float above the zero trip guard of the
// loop and can't execute even if the loop is not reached.
void PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, CountedLoopNode* loop) {
Node* castii = new CastIINode(ctrl, incr, TypeInt::INT, ConstraintCastNode::UnconditionalDependency);
register_new_node(castii, ctrl);
Node* phi = loop->phi();
assert(phi->in(LoopNode::EntryControl) == incr, "replacing wrong input?");
_igvn.replace_input_of(phi, LoopNode::EntryControl, castii);
}
#ifdef ASSERT
void PhaseIdealLoop::ensure_zero_trip_guard_proj(Node* node, bool is_main_loop) {
assert(node->is_IfProj(), "must be the zero trip guard If node");
Node* zer_bol = node->in(0)->in(1);
assert(zer_bol != nullptr && zer_bol->is_Bool(), "must be Bool");
Node* zer_cmp = zer_bol->in(1);
assert(zer_cmp != nullptr && zer_cmp->Opcode() == Op_CmpI, "must be CmpI");
// For the main loop, the opaque node is the second input to zer_cmp, for the post loop it's the first input node
Node* zer_opaq = zer_cmp->in(is_main_loop ? 2 : 1);
assert(zer_opaq != nullptr && zer_opaq->Opcode() == Op_OpaqueZeroTripGuard, "must be OpaqueZeroTripGuard");
}
#endif
//------------------------------insert_pre_post_loops--------------------------
// Insert pre and post loops. If peel_only is set, the pre-loop can not have
// more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
// alignment. Useful to unroll loops that do no array accesses.
void PhaseIdealLoop::insert_pre_post_loops(IdealLoopTree *loop, Node_List &old_new, bool peel_only) {
#ifndef PRODUCT
if (TraceLoopOpts) {
if (peel_only)
tty->print("PeelMainPost ");
else
tty->print("PreMainPost ");
loop->dump_head();
}
#endif
C->set_major_progress();
// Find common pieces of the loop being guarded with pre & post loops
CountedLoopNode *main_head = loop->_head->as_CountedLoop();
assert(main_head->is_normal_loop(), "");
CountedLoopEndNode *main_end = main_head->loopexit();
assert(main_end->outcnt() == 2, "1 true, 1 false path only");
C->print_method(PHASE_BEFORE_PRE_MAIN_POST, 4, main_head);
Node *pre_header= main_head->in(LoopNode::EntryControl);
Node *init = main_head->init_trip();
Node *incr = main_end ->incr();
Node *limit = main_end ->limit();
Node *stride = main_end ->stride();
Node *cmp = main_end ->cmp_node();
BoolTest::mask b_test = main_end->test_trip();
// Need only 1 user of 'bol' because I will be hacking the loop bounds.
Node *bol = main_end->in(CountedLoopEndNode::TestValue);
if (bol->outcnt() != 1) {
bol = bol->clone();
register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
_igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
}
// Need only 1 user of 'cmp' because I will be hacking the loop bounds.
if (cmp->outcnt() != 1) {
cmp = cmp->clone();
register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
_igvn.replace_input_of(bol, 1, cmp);
}
// Add the post loop
CountedLoopNode *post_head = nullptr;
Node* post_incr = incr;
Node* main_exit = insert_post_loop(loop, old_new, main_head, main_end, post_incr, limit, post_head);
//------------------------------
// Step B: Create Pre-Loop.
// Step B1: Clone the loop body. The clone becomes the pre-loop. The main
// loop pre-header illegally has 2 control users (old & new loops).
LoopNode* outer_main_head = main_head;
IdealLoopTree* outer_loop = loop;
if (main_head->is_strip_mined()) {
main_head->verify_strip_mined(1);
outer_main_head = main_head->outer_loop();
outer_loop = loop->_parent;
assert(outer_loop->_head == outer_main_head, "broken loop tree");
}
const uint first_node_index_in_pre_loop_body = Compile::current()->unique();
uint dd_main_head = dom_depth(outer_main_head);
clone_loop(loop, old_new, dd_main_head, ControlAroundStripMined);
CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
pre_head->set_pre_loop(main_head);
Node *pre_incr = old_new[incr->_idx];
// Reduce the pre-loop trip count.
pre_end->_prob = PROB_FAIR;
// Find the pre-loop normal exit.
Node* pre_exit = pre_end->proj_out(false);
assert(pre_exit->Opcode() == Op_IfFalse, "");
IfFalseNode *new_pre_exit = new IfFalseNode(pre_end);
_igvn.register_new_node_with_optimizer(new_pre_exit);
set_idom(new_pre_exit, pre_end, dd_main_head);
set_loop(new_pre_exit, outer_loop->_parent);
// Step B2: Build a zero-trip guard for the main-loop. After leaving the
// pre-loop, the main-loop may not execute at all. Later in life this
// zero-trip guard will become the minimum-trip guard when we unroll
// the main-loop.
Node *min_opaq = new OpaqueZeroTripGuardNode(C, limit, b_test);
Node *min_cmp = new CmpINode(pre_incr, min_opaq);
Node *min_bol = new BoolNode(min_cmp, b_test);
register_new_node(min_opaq, new_pre_exit);
register_new_node(min_cmp , new_pre_exit);
register_new_node(min_bol , new_pre_exit);
// Build the IfNode (assume the main-loop is executed always).
IfNode *min_iff = new IfNode(new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN);
_igvn.register_new_node_with_optimizer(min_iff);
set_idom(min_iff, new_pre_exit, dd_main_head);
set_loop(min_iff, outer_loop->_parent);
// Plug in the false-path, taken if we need to skip main-loop
_igvn.hash_delete(pre_exit);
pre_exit->set_req(0, min_iff);
set_idom(pre_exit, min_iff, dd_main_head);
set_idom(pre_exit->unique_ctrl_out(), min_iff, dd_main_head);
// Make the true-path, must enter the main loop
Node *min_taken = new IfTrueNode(min_iff);
_igvn.register_new_node_with_optimizer(min_taken);
set_idom(min_taken, min_iff, dd_main_head);
set_loop(min_taken, outer_loop->_parent);
// Plug in the true path
_igvn.hash_delete(outer_main_head);
outer_main_head->set_req(LoopNode::EntryControl, min_taken);
set_idom(outer_main_head, min_taken, dd_main_head);
assert(post_head->in(1)->is_IfProj(), "must be zero-trip guard If node projection of the post loop");
VectorSet visited;
Node_Stack clones(main_head->back_control()->outcnt());
// Step B3: Make the fall-in values to the main-loop come from the
// fall-out values of the pre-loop.
const uint last_node_index_in_pre_loop_body = Compile::current()->unique() - 1;
for (DUIterator i2 = main_head->outs(); main_head->has_out(i2); i2++) {
Node* main_phi = main_head->out(i2);
if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0) {
Node* pre_phi = old_new[main_phi->_idx];
Node* fallpre = clone_up_backedge_goo(pre_head->back_control(),
main_head->skip_strip_mined()->in(LoopNode::EntryControl),
pre_phi->in(LoopNode::LoopBackControl),
visited, clones);
_igvn.hash_delete(main_phi);
main_phi->set_req(LoopNode::EntryControl, fallpre);
}
}
DEBUG_ONLY(const uint last_node_index_from_backedge_goo = Compile::current()->unique() - 1);
DEBUG_ONLY(ensure_zero_trip_guard_proj(outer_main_head->in(LoopNode::EntryControl), true);)
initialize_assertion_predicates_for_main_loop(pre_head, main_head, first_node_index_in_pre_loop_body,
last_node_index_in_pre_loop_body,
DEBUG_ONLY(last_node_index_from_backedge_goo COMMA) old_new);
// CastII for the main loop:
cast_incr_before_loop(pre_incr, min_taken, main_head);
// Step B4: Shorten the pre-loop to run only 1 iteration (for now).
// RCE and alignment may change this later.
Node *cmp_end = pre_end->cmp_node();
assert(cmp_end->in(2) == limit, "");
Node *pre_limit = new AddINode(init, stride);
// Save the original loop limit in this Opaque1 node for
// use by range check elimination.
Node *pre_opaq = new Opaque1Node(C, pre_limit, limit);
register_new_node(pre_limit, pre_head->in(LoopNode::EntryControl));
register_new_node(pre_opaq , pre_head->in(LoopNode::EntryControl));
// Since no other users of pre-loop compare, I can hack limit directly
assert(cmp_end->outcnt() == 1, "no other users");
_igvn.hash_delete(cmp_end);
cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
// Special case for not-equal loop bounds:
// Change pre loop test, main loop test, and the
// main loop guard test to use lt or gt depending on stride
// direction:
// positive stride use <
// negative stride use >
//
// not-equal test is kept for post loop to handle case
// when init > limit when stride > 0 (and reverse).
if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
// Modify pre loop end condition
Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test);
register_new_node(new_bol0, pre_head->in(0));
_igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0);
// Modify main loop guard condition
assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test);
register_new_node(new_bol1, new_pre_exit);
_igvn.hash_delete(min_iff);
min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
// Modify main loop end condition
BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test);
register_new_node(new_bol2, main_end->in(CountedLoopEndNode::TestControl));
_igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2);
}
// Flag main loop
main_head->set_main_loop();
if (peel_only) {
main_head->set_main_no_pre_loop();
}
// Subtract a trip count for the pre-loop.
main_head->set_trip_count(main_head->trip_count() - 1);
// It's difficult to be precise about the trip-counts
// for the pre/post loops. They are usually very short,
// so guess that 4 trips is a reasonable value.
post_head->set_profile_trip_cnt(4.0);
pre_head->set_profile_trip_cnt(4.0);
// Now force out all loop-invariant dominating tests. The optimizer
// finds some, but we _know_ they are all useless.
peeled_dom_test_elim(loop,old_new);
loop->record_for_igvn();
C->print_method(PHASE_AFTER_PRE_MAIN_POST, 4, main_head);
}
//------------------------------insert_vector_post_loop------------------------
// Insert a copy of the atomic unrolled vectorized main loop as a post loop,
// unroll_policy has already informed us that more unrolling is about to
// happen to the main loop. The resultant post loop will serve as a
// vectorized drain loop.
void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new) {
if (!loop->_head->is_CountedLoop()) return;
CountedLoopNode *cl = loop->_head->as_CountedLoop();
// only process vectorized main loops
if (!cl->is_vectorized_loop() || !cl->is_main_loop()) return;
int slp_max_unroll_factor = cl->slp_max_unroll();
int cur_unroll = cl->unrolled_count();
if (slp_max_unroll_factor == 0) return;
// only process atomic unroll vector loops (not super unrolled after vectorization)
if (cur_unroll != slp_max_unroll_factor) return;
// we only ever process this one time
if (cl->has_atomic_post_loop()) return;
if (!may_require_nodes(loop->est_loop_clone_sz(2))) {
return;
}
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("PostVector ");
loop->dump_head();
}
#endif
C->set_major_progress();
// Find common pieces of the loop being guarded with pre & post loops
CountedLoopNode *main_head = loop->_head->as_CountedLoop();
CountedLoopEndNode *main_end = main_head->loopexit();
// diagnostic to show loop end is not properly formed
assert(main_end->outcnt() == 2, "1 true, 1 false path only");
// mark this loop as processed
main_head->mark_has_atomic_post_loop();
Node *incr = main_end->incr();
Node *limit = main_end->limit();
// In this case we throw away the result as we are not using it to connect anything else.
CountedLoopNode *post_head = nullptr;
insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head);
// It's difficult to be precise about the trip-counts
// for post loops. They are usually very short,
// so guess that unit vector trips is a reasonable value.
post_head->set_profile_trip_cnt(cur_unroll);
// Now force out all loop-invariant dominating tests. The optimizer
// finds some, but we _know_ they are all useless.
peeled_dom_test_elim(loop, old_new);
loop->record_for_igvn();
}
//------------------------------insert_post_loop-------------------------------
// Insert post loops. Add a post loop to the given loop passed.
Node *PhaseIdealLoop::insert_post_loop(IdealLoopTree* loop, Node_List& old_new,
CountedLoopNode* main_head, CountedLoopEndNode* main_end,
Node* incr, Node* limit, CountedLoopNode*& post_head) {
IfNode* outer_main_end = main_end;
IdealLoopTree* outer_loop = loop;
if (main_head->is_strip_mined()) {
main_head->verify_strip_mined(1);
outer_main_end = main_head->outer_loop_end();
outer_loop = loop->_parent;
assert(outer_loop->_head == main_head->in(LoopNode::EntryControl), "broken loop tree");
}
//------------------------------
// Step A: Create a new post-Loop.
Node* main_exit = outer_main_end->proj_out(false);
assert(main_exit->Opcode() == Op_IfFalse, "");
int dd_main_exit = dom_depth(main_exit);
// Step A1: Clone the loop body of main. The clone becomes the post-loop.
// The main loop pre-header illegally has 2 control users (old & new loops).
const uint first_node_index_in_cloned_loop_body = C->unique();
clone_loop(loop, old_new, dd_main_exit, ControlAroundStripMined);
assert(old_new[main_end->_idx]->Opcode() == Op_CountedLoopEnd, "");
post_head = old_new[main_head->_idx]->as_CountedLoop();
post_head->set_normal_loop();
post_head->set_post_loop(main_head);
// clone_loop() above changes the exit projection
main_exit = outer_main_end->proj_out(false);
// Reduce the post-loop trip count.
CountedLoopEndNode* post_end = old_new[main_end->_idx]->as_CountedLoopEnd();
post_end->_prob = PROB_FAIR;
// Build the main-loop normal exit.
IfFalseNode *new_main_exit = new IfFalseNode(outer_main_end);
_igvn.register_new_node_with_optimizer(new_main_exit);
set_idom(new_main_exit, outer_main_end, dd_main_exit);
set_loop(new_main_exit, outer_loop->_parent);
// Step A2: Build a zero-trip guard for the post-loop. After leaving the
// main-loop, the post-loop may not execute at all. We 'opaque' the incr
// (the previous loop trip-counter exit value) because we will be changing
// the exit value (via additional unrolling) so we cannot constant-fold away the zero
// trip guard until all unrolling is done.
Node *zer_opaq = new OpaqueZeroTripGuardNode(C, incr, main_end->test_trip());
Node *zer_cmp = new CmpINode(zer_opaq, limit);
Node *zer_bol = new BoolNode(zer_cmp, main_end->test_trip());
register_new_node(zer_opaq, new_main_exit);
register_new_node(zer_cmp, new_main_exit);
register_new_node(zer_bol, new_main_exit);
// Build the IfNode
IfNode *zer_iff = new IfNode(new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN);
_igvn.register_new_node_with_optimizer(zer_iff);
set_idom(zer_iff, new_main_exit, dd_main_exit);
set_loop(zer_iff, outer_loop->_parent);
// Plug in the false-path, taken if we need to skip this post-loop
_igvn.replace_input_of(main_exit, 0, zer_iff);
set_idom(main_exit, zer_iff, dd_main_exit);
set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
// Make the true-path, must enter this post loop
Node *zer_taken = new IfTrueNode(zer_iff);
_igvn.register_new_node_with_optimizer(zer_taken);
set_idom(zer_taken, zer_iff, dd_main_exit);
set_loop(zer_taken, outer_loop->_parent);
// Plug in the true path
_igvn.hash_delete(post_head);
post_head->set_req(LoopNode::EntryControl, zer_taken);
set_idom(post_head, zer_taken, dd_main_exit);
VectorSet visited;
Node_Stack clones(main_head->back_control()->outcnt());
// Step A3: Make the fall-in values to the post-loop come from the
// fall-out values of the main-loop.
for (DUIterator i = main_head->outs(); main_head->has_out(i); i++) {
Node* main_phi = main_head->out(i);
if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0) {
Node* cur_phi = old_new[main_phi->_idx];
Node* fallnew = clone_up_backedge_goo(main_head->back_control(),
post_head->init_control(),
main_phi->in(LoopNode::LoopBackControl),
visited, clones);
_igvn.hash_delete(cur_phi);
cur_phi->set_req(LoopNode::EntryControl, fallnew);
}
}
DEBUG_ONLY(ensure_zero_trip_guard_proj(post_head->in(LoopNode::EntryControl), false);)
initialize_assertion_predicates_for_post_loop(main_head, post_head, first_node_index_in_cloned_loop_body);
cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
return new_main_exit;
}
//------------------------------is_invariant-----------------------------
// Return true if n is invariant
bool IdealLoopTree::is_invariant(Node* n) const {
Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
if (n_c->is_top()) return false;
return !is_member(_phase->get_loop(n_c));
}
// Search the Assertion Predicates added by loop predication and/or range check elimination and update them according
// to the new stride.
void PhaseIdealLoop::update_main_loop_assertion_predicates(CountedLoopNode* new_main_loop_head,
const int stride_con_before_unroll) {
// Compute the value of the loop induction variable at the end of the
// first iteration of the unrolled loop: init + new_stride_con - init_inc
int unrolled_stride_con = stride_con_before_unroll * 2;
Node* unrolled_stride = intcon(unrolled_stride_con);
Node* loop_entry = new_main_loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
PredicateIterator predicate_iterator(loop_entry);
UpdateStrideForAssertionPredicates update_stride_for_assertion_predicates(unrolled_stride, new_main_loop_head, this);
predicate_iterator.for_each(update_stride_for_assertion_predicates);
}
// Source Loop: Cloned - peeled_loop_head
// Target Loop: Original - remaining_loop_head
void PhaseIdealLoop::initialize_assertion_predicates_for_peeled_loop(CountedLoopNode* peeled_loop_head,
CountedLoopNode* remaining_loop_head,
const uint first_node_index_in_cloned_loop_body,
const Node_List& old_new) {
const NodeInOriginalLoopBody node_in_original_loop_body(first_node_index_in_cloned_loop_body, old_new);
create_assertion_predicates_at_loop(peeled_loop_head, remaining_loop_head, node_in_original_loop_body, true);
}
// Source Loop: Cloned - pre_loop_head
// Target Loop: Original - main_loop_head
void PhaseIdealLoop::initialize_assertion_predicates_for_main_loop(CountedLoopNode* pre_loop_head,
CountedLoopNode* main_loop_head,
const uint first_node_index_in_pre_loop_body,
const uint last_node_index_in_pre_loop_body,
DEBUG_ONLY(const uint last_node_index_from_backedge_goo COMMA)
const Node_List& old_new) {
assert(first_node_index_in_pre_loop_body < last_node_index_in_pre_loop_body, "cloned some nodes");
const NodeInMainLoopBody node_in_main_loop_body(first_node_index_in_pre_loop_body,
last_node_index_in_pre_loop_body,
DEBUG_ONLY(last_node_index_from_backedge_goo COMMA) old_new);
create_assertion_predicates_at_main_or_post_loop(pre_loop_head, main_loop_head, node_in_main_loop_body, true);
}
// Source Loop: Original - main_loop_head
// Target Loop: Cloned - post_loop_head
//
// The post loop is cloned before the pre loop. Do not kill the old Template Assertion Predicates, yet. We need to clone
// from them when creating the pre loop. Only then we can kill them.
void PhaseIdealLoop::initialize_assertion_predicates_for_post_loop(CountedLoopNode* main_loop_head,
CountedLoopNode* post_loop_head,
const uint first_node_index_in_cloned_loop_body) {
const NodeInClonedLoopBody node_in_cloned_loop_body(first_node_index_in_cloned_loop_body);
create_assertion_predicates_at_main_or_post_loop(main_loop_head, post_loop_head, node_in_cloned_loop_body, false);
}
void PhaseIdealLoop::create_assertion_predicates_at_loop(CountedLoopNode* source_loop_head,
CountedLoopNode* target_loop_head,
const NodeInLoopBody& _node_in_loop_body,
const bool kill_old_template) {
CreateAssertionPredicatesVisitor create_assertion_predicates_visitor(target_loop_head, this, _node_in_loop_body,
kill_old_template);
Node* source_loop_entry = source_loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
PredicateIterator predicate_iterator(source_loop_entry);
predicate_iterator.for_each(create_assertion_predicates_visitor);
}
void PhaseIdealLoop::create_assertion_predicates_at_main_or_post_loop(CountedLoopNode* source_loop_head,
CountedLoopNode* target_loop_head,
const NodeInLoopBody& _node_in_loop_body,
const bool kill_old_template) {
Node* old_target_loop_head_entry = target_loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
const uint node_index_before_new_assertion_predicate_nodes = C->unique();
const bool need_to_rewire_old_target_loop_entry_dependencies = old_target_loop_head_entry->outcnt() > 1;
create_assertion_predicates_at_loop(source_loop_head, target_loop_head, _node_in_loop_body, kill_old_template);
if (need_to_rewire_old_target_loop_entry_dependencies) {
rewire_old_target_loop_entry_dependency_to_new_entry(target_loop_head, old_target_loop_head_entry,
node_index_before_new_assertion_predicate_nodes);
}
}
// Rewire any control dependent nodes on the old target loop entry before adding Assertion Predicate related nodes.
// These have been added by PhaseIdealLoop::clone_up_backedge_goo() and assume to be ending up at the target loop entry
// which is no longer the case when adding additional Assertion Predicates. Fix this by rewiring these nodes to the new
// target loop entry which corresponds to the tail of the last Assertion Predicate before the target loop. This is safe
// to do because these control dependent nodes on the old target loop entry created by clone_up_backedge_goo() were
// pinned on the loop backedge before. The Assertion Predicates are not control dependent on these nodes in any way.
void PhaseIdealLoop::rewire_old_target_loop_entry_dependency_to_new_entry(
CountedLoopNode* target_loop_head, const Node* old_target_loop_entry,
const uint node_index_before_new_assertion_predicate_nodes) {
Node* new_main_loop_entry = target_loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
if (new_main_loop_entry == old_target_loop_entry) {
// No Assertion Predicates added.
return;
}
for (DUIterator_Fast imax, i = old_target_loop_entry->fast_outs(imax); i < imax; i++) {
Node* out = old_target_loop_entry->fast_out(i);
if (!out->is_CFG() && out->_idx < node_index_before_new_assertion_predicate_nodes) {
assert(out != target_loop_head->init_trip(), "CastII on loop entry?");
_igvn.replace_input_of(out, 0, new_main_loop_entry);
set_ctrl(out, new_main_loop_entry);
--i;
--imax;
}
}
}
//------------------------------do_unroll--------------------------------------
// Unroll the loop body one step - make each trip do 2 iterations.
void PhaseIdealLoop::do_unroll(IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip) {
assert(LoopUnrollLimit, "");
CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
CountedLoopEndNode *loop_end = loop_head->loopexit();
C->print_method(PHASE_BEFORE_LOOP_UNROLLING, 4, loop_head);
#ifndef PRODUCT
if (TraceLoopOpts) {
if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
} else {
tty->print("Unroll %d ", loop_head->unrolled_count()*2);
}
loop->dump_head();
}
if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) {
Node_Stack stack(C->live_nodes() >> 2);
Node_List rpo_list;
VectorSet visited;
visited.set(loop_head->_idx);
rpo(loop_head, stack, visited, rpo_list);
dump(loop, rpo_list.size(), rpo_list);
}
#endif
// Remember loop node count before unrolling to detect
// if rounds of unroll,optimize are making progress
loop_head->set_node_count_before_unroll(loop->_body.size());
Node *ctrl = loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
Node *limit = loop_head->limit();
Node *init = loop_head->init_trip();
Node *stride = loop_head->stride();
Node *opaq = nullptr;
if (adjust_min_trip) { // If not maximally unrolling, need adjustment
// Search for zero-trip guard.
// Check the shape of the graph at the loop entry. If an inappropriate
// graph shape is encountered, the compiler bails out loop unrolling;
// compilation of the method will still succeed.
opaq = loop_head->is_canonical_loop_entry();
if (opaq == nullptr) {
return;
}
// Zero-trip test uses an 'opaque' node which is not shared.
assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
}
C->set_major_progress();
Node* new_limit = nullptr;
const int stride_con = stride->get_int();
int stride_p = (stride_con > 0) ? stride_con : -stride_con;
uint old_trip_count = loop_head->trip_count();
// Verify that unroll policy result is still valid.
assert(old_trip_count > 1 && (!adjust_min_trip || stride_p <=
MIN2<int>(max_jint / 2 - 2, MAX2(1<<3, Matcher::max_vector_size(T_BYTE)) * loop_head->unrolled_count())), "sanity");
// Adjust loop limit to keep valid iterations number after unroll.
// Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
// which may overflow.
if (!adjust_min_trip) {
assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
"odd trip count for maximally unroll");
// Don't need to adjust limit for maximally unroll since trip count is even.
} else if (loop_head->has_exact_trip_count() && init->is_Con()) {
// The trip count being exact means it has been set (using CountedLoopNode::set_exact_trip_count in compute_trip_count)
assert(old_trip_count < max_juint, "sanity");
// Loop's limit is constant. Loop's init could be constant when pre-loop
// become peeled iteration.
jlong init_con = init->get_int();
// We can keep old loop limit if iterations count stays the same:
// old_trip_count == new_trip_count * 2
// Note: since old_trip_count >= 2 then new_trip_count >= 1
// so we also don't need to adjust zero trip test.
jlong limit_con = limit->get_int();
// (stride_con*2) not overflow since stride_con <= 8.
int new_stride_con = stride_con * 2;
int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1);
jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
// New trip count should satisfy next conditions.
assert(trip_count > 0 && (julong)trip_count <= (julong)max_juint/2, "sanity");
uint new_trip_count = (uint)trip_count;
// Since old_trip_count has been set to < max_juint (that is at most 2^32-2),
// new_trip_count is lower than or equal to 2^31-1 and the multiplication cannot overflow.
adjust_min_trip = (old_trip_count != new_trip_count*2);
}
if (adjust_min_trip) {
// Step 2: Adjust the trip limit if it is called for.
// The adjustment amount is -stride. Need to make sure if the
// adjustment underflows or overflows, then the main loop is skipped.
Node* cmp = loop_end->cmp_node();
assert(cmp->in(2) == limit, "sanity");
assert(opaq != nullptr && opaq->in(1) == limit, "sanity");
// Verify that policy_unroll result is still valid.
const TypeInt* limit_type = _igvn.type(limit)->is_int();
assert((stride_con > 0 && ((min_jint + stride_con) <= limit_type->_hi)) ||
(stride_con < 0 && ((max_jint + stride_con) >= limit_type->_lo)),
"sanity");
if (limit->is_Con()) {
// The check in policy_unroll and the assert above guarantee
// no underflow if limit is constant.
new_limit = intcon(limit->get_int() - stride_con);
} else {
// Limit is not constant. Int subtraction could lead to underflow.
// (1) Convert to long.
Node* limit_l = new ConvI2LNode(limit);
register_new_node_with_ctrl_of(limit_l, limit);
Node* stride_l = longcon(stride_con);
// (2) Subtract: compute in long, to prevent underflow.
Node* new_limit_l = new SubLNode(limit_l, stride_l);
register_new_node(new_limit_l, ctrl);
// (3) Clamp to int range, in case we had subtraction underflow.
Node* underflow_clamp_l = longcon((stride_con > 0) ? min_jint : max_jint);
Node* new_limit_no_underflow_l = nullptr;
if (stride_con > 0) {
// limit = MaxL(limit - stride, min_jint)
new_limit_no_underflow_l = new MaxLNode(C, new_limit_l, underflow_clamp_l);
} else {
// limit = MinL(limit - stride, max_jint)
new_limit_no_underflow_l = new MinLNode(C, new_limit_l, underflow_clamp_l);
}
register_new_node(new_limit_no_underflow_l, ctrl);
// (4) Convert back to int.
new_limit = new ConvL2INode(new_limit_no_underflow_l);
register_new_node(new_limit, ctrl);
}
assert(new_limit != nullptr, "");
// Replace in loop test.
assert(loop_end->in(1)->in(1) == cmp, "sanity");
if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
// Don't need to create new test since only one user.
_igvn.hash_delete(cmp);
cmp->set_req(2, new_limit);
} else {
// Create new test since it is shared.
Node* ctrl2 = loop_end->in(0);
Node* cmp2 = cmp->clone();
cmp2->set_req(2, new_limit);
register_new_node(cmp2, ctrl2);
Node* bol2 = loop_end->in(1)->clone();
bol2->set_req(1, cmp2);
register_new_node(bol2, ctrl2);
_igvn.replace_input_of(loop_end, 1, bol2);
}
// Step 3: Find the min-trip test guaranteed before a 'main' loop.
// Make it a 1-trip test (means at least 2 trips).
// Guard test uses an 'opaque' node which is not shared. Hence I
// can edit it's inputs directly. Hammer in the new limit for the
// minimum-trip guard.
assert(opaq->outcnt() == 1, "");
// Notify limit -> opaq -> CmpI, it may constant fold.
_igvn.add_users_to_worklist(opaq->in(1));
_igvn.replace_input_of(opaq, 1, new_limit);
}
// Adjust max trip count. The trip count is intentionally rounded
// down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
// the main, unrolled, part of the loop will never execute as it is protected
// by the min-trip test. See bug 4834191 for a case where we over-unrolled
// and later determined that part of the unrolled loop was dead.
loop_head->set_trip_count(old_trip_count / 2);
// Double the count of original iterations in the unrolled loop body.
loop_head->double_unrolled_count();
// ---------
// Step 4: Clone the loop body. Move it inside the loop. This loop body
// represents the odd iterations; since the loop trips an even number of
// times its backedge is never taken. Kill the backedge.
uint dd = dom_depth(loop_head);
clone_loop(loop, old_new, dd, IgnoreStripMined);
// Make backedges of the clone equal to backedges of the original.
// Make the fall-in from the original come from the fall-out of the clone.
for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
Node* phi = loop_head->fast_out(j);
if (phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0) {
Node *newphi = old_new[phi->_idx];
_igvn.hash_delete(phi);
_igvn.hash_delete(newphi);
phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
phi ->set_req(LoopNode::LoopBackControl, C->top());
}
}
CountedLoopNode* clone_head = old_new[loop_head->_idx]->as_CountedLoop();
_igvn.hash_delete(clone_head);
loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
loop_head ->set_req(LoopNode::LoopBackControl, C->top());
loop->_head = clone_head; // New loop header
set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
// Kill the clone's backedge
Node *newcle = old_new[loop_end->_idx];
_igvn.hash_delete(newcle);
Node* one = intcon(1);
newcle->set_req(1, one);
// Force clone into same loop body
uint max = loop->_body.size();
for (uint k = 0; k < max; k++) {
Node *old = loop->_body.at(k);
Node *nnn = old_new[old->_idx];
loop->_body.push(nnn);
if (!has_ctrl(old)) {
set_loop(nnn, loop);
}
}
loop->record_for_igvn();
loop_head->clear_strip_mined();
update_main_loop_assertion_predicates(clone_head, stride_con);
#ifndef PRODUCT
if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) {
tty->print("\nnew loop after unroll\n"); loop->dump_head();
for (uint i = 0; i < loop->_body.size(); i++) {
loop->_body.at(i)->dump();
}
if (C->clone_map().is_debug()) {
tty->print("\nCloneMap\n");
Dict* dict = C->clone_map().dict();
DictI i(dict);
tty->print_cr("Dict@%p[%d] = ", dict, dict->Size());
for (int ii = 0; i.test(); ++i, ++ii) {
NodeCloneInfo cl((uint64_t)dict->operator[]((void*)i._key));
tty->print("%d->%d:%d,", (int)(intptr_t)i._key, cl.idx(), cl.gen());
if (ii % 10 == 9) {
tty->print_cr(" ");
}
}
tty->print_cr(" ");
}
}
#endif
C->print_method(PHASE_AFTER_LOOP_UNROLLING, 4, clone_head);
}
//------------------------------do_maximally_unroll----------------------------
void PhaseIdealLoop::do_maximally_unroll(IdealLoopTree *loop, Node_List &old_new) {
CountedLoopNode *cl = loop->_head->as_CountedLoop();
assert(cl->has_exact_trip_count(), "trip count is not exact");
assert(cl->trip_count() > 0, "");
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("MaxUnroll %d ", cl->trip_count());
loop->dump_head();
}
#endif
// If loop is tripping an odd number of times, peel odd iteration
if ((cl->trip_count() & 1) == 1) {
do_peeling(loop, old_new);
}
// Now its tripping an even number of times remaining. Double loop body.
// Do not adjust pre-guards; they are not needed and do not exist.
if (cl->trip_count() > 0) {
assert((cl->trip_count() & 1) == 0, "missed peeling");
do_unroll(loop, old_new, false);
}
}
//------------------------------adjust_limit-----------------------------------
// Helper function that computes new loop limit as (rc_limit-offset)/scale
Node* PhaseIdealLoop::adjust_limit(bool is_positive_stride, Node* scale, Node* offset, Node* rc_limit, Node* old_limit, Node* pre_ctrl, bool round) {
Node* old_limit_long = new ConvI2LNode(old_limit);
register_new_node(old_limit_long, pre_ctrl);
Node* sub = new SubLNode(rc_limit, offset);
register_new_node(sub, pre_ctrl);
Node* limit = new DivLNode(nullptr, sub, scale);
register_new_node(limit, pre_ctrl);
// When the absolute value of scale is greater than one, the division
// may round limit down/up, so add/sub one to/from the limit.
if (round) {
limit = new AddLNode(limit, _igvn.longcon(is_positive_stride ? -1 : 1));
register_new_node(limit, pre_ctrl);
}
// Clamp the limit to handle integer under-/overflows by using long values.
// We only convert the limit back to int when we handled under-/overflows.
// Note that all values are longs in the following computations.
// When reducing the limit, clamp to [min_jint, old_limit]:
// INT(MINL(old_limit, MAXL(limit, min_jint)))
// - integer underflow of limit: MAXL chooses min_jint.
// - integer overflow of limit: MINL chooses old_limit (<= MAX_INT < limit)
// When increasing the limit, clamp to [old_limit, max_jint]:
// INT(MAXL(old_limit, MINL(limit, max_jint)))
// - integer overflow of limit: MINL chooses max_jint.
// - integer underflow of limit: MAXL chooses old_limit (>= MIN_INT > limit)
// INT() is finally converting the limit back to an integer value.
Node* inner_result_long = nullptr;
Node* outer_result_long = nullptr;
if (is_positive_stride) {
inner_result_long = new MaxLNode(C, limit, _igvn.longcon(min_jint));
outer_result_long = new MinLNode(C, inner_result_long, old_limit_long);
} else {
inner_result_long = new MinLNode(C, limit, _igvn.longcon(max_jint));
outer_result_long = new MaxLNode(C, inner_result_long, old_limit_long);
}
register_new_node(inner_result_long, pre_ctrl);
register_new_node(outer_result_long, pre_ctrl);
limit = new ConvL2INode(outer_result_long);
register_new_node(limit, pre_ctrl);
return limit;
}
//------------------------------add_constraint---------------------------------
// Constrain the main loop iterations so the conditions:
// low_limit <= scale_con*I + offset < upper_limit
// always hold true. That is, either increase the number of iterations in the
// pre-loop or reduce the number of iterations in the main-loop until the condition
// holds true in the main-loop. Stride, scale, offset and limit are all loop
// invariant. Further, stride and scale are constants (offset and limit often are).
void PhaseIdealLoop::add_constraint(jlong stride_con, jlong scale_con, Node* offset, Node* low_limit, Node* upper_limit, Node* pre_ctrl, Node** pre_limit, Node** main_limit) {
assert(_igvn.type(offset)->isa_long() != nullptr && _igvn.type(low_limit)->isa_long() != nullptr &&
_igvn.type(upper_limit)->isa_long() != nullptr, "arguments should be long values");
// For a positive stride, we need to reduce the main-loop limit and
// increase the pre-loop limit. This is reversed for a negative stride.
bool is_positive_stride = (stride_con > 0);
// If the absolute scale value is greater one, division in 'adjust_limit' may require
// rounding. Make sure the ABS method correctly handles min_jint.
// Only do this for the pre-loop, one less iteration of the main loop doesn't hurt.
bool round = ABS(scale_con) > 1;
Node* scale = longcon(scale_con);
if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
// Positive stride*scale: the affine function is increasing,
// the pre-loop checks for underflow and the post-loop for overflow.
// The overflow limit: scale*I+offset < upper_limit
// For the main-loop limit compute:
// ( if (scale > 0) /* and stride > 0 */
// I < (upper_limit-offset)/scale
// else /* scale < 0 and stride < 0 */
// I > (upper_limit-offset)/scale
// )
*main_limit = adjust_limit(is_positive_stride, scale, offset, upper_limit, *main_limit, pre_ctrl, false);
// The underflow limit: low_limit <= scale*I+offset
// For the pre-loop limit compute:
// NOT(scale*I+offset >= low_limit)
// scale*I+offset < low_limit
// ( if (scale > 0) /* and stride > 0 */
// I < (low_limit-offset)/scale
// else /* scale < 0 and stride < 0 */
// I > (low_limit-offset)/scale
// )
*pre_limit = adjust_limit(!is_positive_stride, scale, offset, low_limit, *pre_limit, pre_ctrl, round);
} else {
// Negative stride*scale: the affine function is decreasing,
// the pre-loop checks for overflow and the post-loop for underflow.
// The overflow limit: scale*I+offset < upper_limit
// For the pre-loop limit compute:
// NOT(scale*I+offset < upper_limit)
// scale*I+offset >= upper_limit
// scale*I+offset+1 > upper_limit
// ( if (scale < 0) /* and stride > 0 */
// I < (upper_limit-(offset+1))/scale
// else /* scale > 0 and stride < 0 */
// I > (upper_limit-(offset+1))/scale
// )
Node* one = longcon(1);
Node* plus_one = new AddLNode(offset, one);
register_new_node(plus_one, pre_ctrl);
*pre_limit = adjust_limit(!is_positive_stride, scale, plus_one, upper_limit, *pre_limit, pre_ctrl, round);
// The underflow limit: low_limit <= scale*I+offset
// For the main-loop limit compute:
// scale*I+offset+1 > low_limit
// ( if (scale < 0) /* and stride > 0 */
// I < (low_limit-(offset+1))/scale
// else /* scale > 0 and stride < 0 */
// I > (low_limit-(offset+1))/scale
// )
*main_limit = adjust_limit(is_positive_stride, scale, plus_one, low_limit, *main_limit, pre_ctrl, false);
}
}
//----------------------------------is_iv------------------------------------
// Return true if exp is the value (of type bt) of the given induction var.
// This grammar of cases is recognized, where X is I|L according to bt:
// VIV[iv] = iv | (CastXX VIV[iv]) | (ConvI2X VIV[iv])
bool PhaseIdealLoop::is_iv(Node* exp, Node* iv, BasicType bt) {
exp = exp->uncast();
if (exp == iv && iv->bottom_type()->isa_integer(bt)) {
return true;
}
if (bt == T_LONG && iv->bottom_type()->isa_int() && exp->Opcode() == Op_ConvI2L && exp->in(1)->uncast() == iv) {
return true;
}
return false;
}
//------------------------------is_scaled_iv---------------------------------
// Return true if exp is a constant times the given induction var (of type bt).
// The multiplication is either done in full precision (exactly of type bt),
// or else bt is T_LONG but iv is scaled using 32-bit arithmetic followed by a ConvI2L.
// This grammar of cases is recognized, where X is I|L according to bt:
// SIV[iv] = VIV[iv] | (CastXX SIV[iv])
// | (MulX VIV[iv] ConX) | (MulX ConX VIV[iv])
// | (LShiftX VIV[iv] ConI)
// | (ConvI2L SIV[iv]) -- a "short-scale" can occur here; note recursion
// | (SubX 0 SIV[iv]) -- same as MulX(iv, -scale); note recursion
// | (AddX SIV[iv] SIV[iv]) -- sum of two scaled iv; note recursion
// | (SubX SIV[iv] SIV[iv]) -- difference of two scaled iv; note recursion
// VIV[iv] = [either iv or its value converted; see is_iv() above]
// On success, the constant scale value is stored back to *p_scale.
// The value (*p_short_scale) reports if such a ConvI2L conversion was present.
bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, BasicType bt, jlong* p_scale, bool* p_short_scale, int depth) {
BasicType exp_bt = bt;
exp = exp->uncast(); //strip casts
assert(exp_bt == T_INT || exp_bt == T_LONG, "unexpected int type");
if (is_iv(exp, iv, exp_bt)) {
if (p_scale != nullptr) {
*p_scale = 1;
}
if (p_short_scale != nullptr) {
*p_short_scale = false;
}
return true;
}
if (exp_bt == T_LONG && iv->bottom_type()->isa_int() && exp->Opcode() == Op_ConvI2L) {
exp = exp->in(1);
exp_bt = T_INT;
}
int opc = exp->Opcode();
int which = 0; // this is which subexpression we find the iv in
// Can't use is_Mul() here as it's true for AndI and AndL
if (opc == Op_Mul(exp_bt)) {
if ((is_iv(exp->in(which = 1), iv, exp_bt) && exp->in(2)->is_Con()) ||
(is_iv(exp->in(which = 2), iv, exp_bt) && exp->in(1)->is_Con())) {
Node* factor = exp->in(which == 1 ? 2 : 1); // the other argument
jlong scale = factor->find_integer_as_long(exp_bt, 0);
if (scale == 0) {
return false; // might be top
}
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_short_scale != nullptr) {
// (ConvI2L (MulI iv K)) can be 64-bit linear if iv is kept small enough...
*p_short_scale = (exp_bt != bt && scale != 1);
}
return true;
}
} else if (opc == Op_LShift(exp_bt)) {
if (is_iv(exp->in(1), iv, exp_bt) && exp->in(2)->is_Con()) {
jint shift_amount = exp->in(2)->find_int_con(min_jint);
if (shift_amount == min_jint) {
return false; // might be top
}
jlong scale;
if (exp_bt == T_INT) {
scale = java_shift_left((jint)1, (juint)shift_amount);
} else if (exp_bt == T_LONG) {
scale = java_shift_left((jlong)1, (julong)shift_amount);
}
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_short_scale != nullptr) {
// (ConvI2L (MulI iv K)) can be 64-bit linear if iv is kept small enough...
*p_short_scale = (exp_bt != bt && scale != 1);
}
return true;
}
} else if (opc == Op_Add(exp_bt)) {
jlong scale_l = 0;
jlong scale_r = 0;
bool short_scale_l = false;
bool short_scale_r = false;
if (depth == 0 &&
is_scaled_iv(exp->in(1), iv, exp_bt, &scale_l, &short_scale_l, depth + 1) &&
is_scaled_iv(exp->in(2), iv, exp_bt, &scale_r, &short_scale_r, depth + 1)) {
// AddX(iv*K1, iv*K2) => iv*(K1+K2)
jlong scale_sum = java_add(scale_l, scale_r);
if (scale_sum > max_signed_integer(exp_bt) || scale_sum <= min_signed_integer(exp_bt)) {
// This logic is shared by int and long. For int, the result may overflow
// as we use jlong to compute so do the check here. Long result may also
// overflow but that's fine because result wraps.
return false;
}
if (p_scale != nullptr) {
*p_scale = scale_sum;
}
if (p_short_scale != nullptr) {
*p_short_scale = short_scale_l && short_scale_r;
}
return true;
}
} else if (opc == Op_Sub(exp_bt)) {
if (exp->in(1)->find_integer_as_long(exp_bt, -1) == 0) {
jlong scale = 0;
if (depth == 0 && is_scaled_iv(exp->in(2), iv, exp_bt, &scale, p_short_scale, depth + 1)) {
// SubX(0, iv*K) => iv*(-K)
if (scale == min_signed_integer(exp_bt)) {
// This should work even if -K overflows, but let's not.
return false;
}
scale = java_multiply(scale, (jlong)-1);
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_short_scale != nullptr) {
// (ConvI2L (MulI iv K)) can be 64-bit linear if iv is kept small enough...
*p_short_scale = *p_short_scale || (exp_bt != bt && scale != 1);
}
return true;
}
} else {
jlong scale_l = 0;
jlong scale_r = 0;
bool short_scale_l = false;
bool short_scale_r = false;
if (depth == 0 &&
is_scaled_iv(exp->in(1), iv, exp_bt, &scale_l, &short_scale_l, depth + 1) &&
is_scaled_iv(exp->in(2), iv, exp_bt, &scale_r, &short_scale_r, depth + 1)) {
// SubX(iv*K1, iv*K2) => iv*(K1-K2)
jlong scale_diff = java_subtract(scale_l, scale_r);
if (scale_diff > max_signed_integer(exp_bt) || scale_diff <= min_signed_integer(exp_bt)) {
// This logic is shared by int and long. For int, the result may
// overflow as we use jlong to compute so do the check here. Long
// result may also overflow but that's fine because result wraps.
return false;
}
if (p_scale != nullptr) {
*p_scale = scale_diff;
}
if (p_short_scale != nullptr) {
*p_short_scale = short_scale_l && short_scale_r;
}
return true;
}
}
}
// We could also recognize (iv*K1)*K2, even with overflow, but let's not.
return false;
}
//-------------------------is_scaled_iv_plus_offset--------------------------
// Return true if exp is a simple linear transform of the given induction var.
// The scale must be constant and the addition tree (if any) must be simple.
// This grammar of cases is recognized, where X is I|L according to bt:
//
// OIV[iv] = SIV[iv] | (CastXX OIV[iv])
// | (AddX SIV[iv] E) | (AddX E SIV[iv])
// | (SubX SIV[iv] E) | (SubX E SIV[iv])
// SSIV[iv] = (ConvI2X SIV[iv]) -- a "short scale" might occur here
// SIV[iv] = [a possibly scaled value of iv; see is_scaled_iv() above]
//
// On success, the constant scale value is stored back to *p_scale unless null.
// Likewise, the addend (perhaps a synthetic AddX node) is stored to *p_offset.
// Also, (*p_short_scale) reports if a ConvI2L conversion was seen after a MulI,
// meaning bt is T_LONG but iv was scaled using 32-bit arithmetic.
// To avoid looping, the match is depth-limited, and so may fail to match the grammar to complex expressions.
bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, BasicType bt, jlong* p_scale, Node** p_offset, bool* p_short_scale, int depth) {
assert(bt == T_INT || bt == T_LONG, "unexpected int type");
jlong scale = 0; // to catch result from is_scaled_iv()
BasicType exp_bt = bt;
exp = exp->uncast();
if (is_scaled_iv(exp, iv, exp_bt, &scale, p_short_scale)) {
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_offset != nullptr) {
Node* zero = zerocon(bt);
*p_offset = zero;
}
return true;
}
if (exp_bt != bt) {
// We would now be matching inputs like (ConvI2L exp:(AddI (MulI iv S) E)).
// It's hard to make 32-bit arithmetic linear if it overflows. Although we do
// cope with overflowing multiplication by S, it would be even more work to
// handle overflowing addition of E. So we bail out here on ConvI2L input.
return false;
}
int opc = exp->Opcode();
int which = 0; // this is which subexpression we find the iv in
Node* offset = nullptr;
if (opc == Op_Add(exp_bt)) {
// Check for a scaled IV in (AddX (MulX iv S) E) or (AddX E (MulX iv S)).
if (is_scaled_iv(exp->in(which = 1), iv, bt, &scale, p_short_scale) ||
is_scaled_iv(exp->in(which = 2), iv, bt, &scale, p_short_scale)) {
offset = exp->in(which == 1 ? 2 : 1); // the other argument
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_offset != nullptr) {
*p_offset = offset;
}
return true;
}
// Check for more addends, like (AddX (AddX (MulX iv S) E1) E2), etc.
if (is_scaled_iv_plus_extra_offset(exp->in(1), exp->in(2), iv, bt, p_scale, p_offset, p_short_scale, depth) ||
is_scaled_iv_plus_extra_offset(exp->in(2), exp->in(1), iv, bt, p_scale, p_offset, p_short_scale, depth)) {
return true;
}
} else if (opc == Op_Sub(exp_bt)) {
if (is_scaled_iv(exp->in(which = 1), iv, bt, &scale, p_short_scale) ||
is_scaled_iv(exp->in(which = 2), iv, bt, &scale, p_short_scale)) {
// Match (SubX SIV[iv] E) as if (AddX SIV[iv] (SubX 0 E)), and
// match (SubX E SIV[iv]) as if (AddX E (SubX 0 SIV[iv])).
offset = exp->in(which == 1 ? 2 : 1); // the other argument
if (which == 2) {
// We can't handle a scale of min_jint (or min_jlong) here as -1 * min_jint = min_jint
if (scale == min_signed_integer(bt)) {
return false; // cannot negate the scale of the iv
}
scale = java_multiply(scale, (jlong)-1);
}
if (p_scale != nullptr) {
*p_scale = scale;
}
if (p_offset != nullptr) {
if (which == 1) { // must negate the extracted offset
Node* zero = integercon(0, exp_bt);
Node *ctrl_off = get_ctrl(offset);
offset = SubNode::make(zero, offset, exp_bt);
register_new_node(offset, ctrl_off);
}
*p_offset = offset;
}
return true;
}
}
return false;
}
// Helper for is_scaled_iv_plus_offset(), not called separately.
// The caller encountered (AddX exp1 offset3) or (AddX offset3 exp1).
// Here, exp1 is inspected to see if it is a simple linear transform of iv.
// If so, the offset3 is combined with any other offset2 from inside exp1.
bool PhaseIdealLoop::is_scaled_iv_plus_extra_offset(Node* exp1, Node* offset3, Node* iv,
BasicType bt,
jlong* p_scale, Node** p_offset,
bool* p_short_scale, int depth) {
// By the time we reach here, it is unlikely that exp1 is a simple iv*K.
// If is a linear iv transform, it is probably an add or subtract.
// Let's collect the internal offset2 from it.
Node* offset2 = nullptr;
if (offset3->is_Con() &&
depth < 2 &&
is_scaled_iv_plus_offset(exp1, iv, bt, p_scale,
&offset2, p_short_scale, depth+1)) {
if (p_offset != nullptr) {
Node* ctrl_off2 = get_ctrl(offset2);
Node* offset = AddNode::make(offset2, offset3, bt);
register_new_node(offset, ctrl_off2);
*p_offset = offset;
}
return true;
}
return false;
}
//------------------------------do_range_check---------------------------------
// Eliminate range-checks and other trip-counter vs loop-invariant tests.
void PhaseIdealLoop::do_range_check(IdealLoopTree* loop) {
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("RangeCheck ");
loop->dump_head();
}
#endif
assert(RangeCheckElimination, "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
// protect against stride not being a constant
if (!cl->stride_is_con()) {
return;
}
// Find the trip counter; we are iteration splitting based on it
Node *trip_counter = cl->phi();
// Find the main loop limit; we will trim it's iterations
// to not ever trip end tests
Node *main_limit = cl->limit();
Node* main_limit_ctrl = get_ctrl(main_limit);
// Check graph shape. Cannot optimize a loop if zero-trip
// Opaque1 node is optimized away and then another round
// of loop opts attempted.
if (cl->is_canonical_loop_entry() == nullptr) {
return;
}
// Need to find the main-loop zero-trip guard
Node *ctrl = cl->skip_assertion_predicates_with_halt();
Node *iffm = ctrl->in(0);
Node *opqzm = iffm->in(1)->in(1)->in(2);
assert(opqzm->in(1) == main_limit, "do not understand situation");
// Find the pre-loop limit; we will expand its iterations to
// not ever trip low tests.
Node *p_f = iffm->in(0);
// pre loop may have been optimized out
if (p_f->Opcode() != Op_IfFalse) {
return;
}
CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
assert(pre_end->loopnode()->is_pre_loop(), "");
Node *pre_opaq1 = pre_end->limit();
// Occasionally it's possible for a pre-loop Opaque1 node to be
// optimized away and then another round of loop opts attempted.
// We can not optimize this particular loop in that case.
if (pre_opaq1->Opcode() != Op_Opaque1) {
return;
}
Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
Node *pre_limit = pre_opaq->in(1);
Node* pre_limit_ctrl = get_ctrl(pre_limit);
// Where do we put new limit calculations
Node* pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
// Range check elimination optimizes out conditions whose parameters are loop invariant in the main loop. They usually
// have control above the pre loop, but there's no guarantee that they do. There's no guarantee either that the pre
// loop limit has control that's out of loop (a previous round of range check elimination could have set a limit that's
// not loop invariant). new_limit_ctrl is used for both the pre and main loops. Early control for the main limit may be
// below the pre loop entry and the pre limit and must be taken into account when initializing new_limit_ctrl.
Node* new_limit_ctrl = dominated_node(pre_ctrl, pre_limit_ctrl, compute_early_ctrl(main_limit, main_limit_ctrl));
// Ensure the original loop limit is available from the
// pre-loop Opaque1 node.
Node *orig_limit = pre_opaq->original_loop_limit();
if (orig_limit == nullptr || _igvn.type(orig_limit) == Type::TOP) {
return;
}
// Must know if its a count-up or count-down loop
int stride_con = cl->stride_con();
bool abs_stride_is_one = stride_con == 1 || stride_con == -1;
Node* zero = longcon(0);
Node* one = longcon(1);
// Use symmetrical int range [-max_jint,max_jint]
Node* mini = longcon(-max_jint);
Node* loop_entry = cl->skip_strip_mined()->in(LoopNode::EntryControl);
assert(loop_entry->is_Proj() && loop_entry->in(0)->is_If(), "if projection only");
// if abs(stride) == 1, an Assertion Predicate for the final iv value is added. We don't know the final iv value until
// we're done with range check elimination so use a place holder.
Node* final_iv_placeholder = nullptr;
if (abs_stride_is_one) {
final_iv_placeholder = new Node(1);
_igvn.set_type(final_iv_placeholder, TypeInt::INT);
final_iv_placeholder->init_req(0, loop_entry);
}
// Check loop body for tests of trip-counter plus loop-invariant vs loop-variant.
for (uint i = 0; i < loop->_body.size(); i++) {
Node *iff = loop->_body[i];
if (iff->Opcode() == Op_If ||
iff->Opcode() == Op_RangeCheck) { // Test?
// Test is an IfNode, has 2 projections. If BOTH are in the loop
// we need loop unswitching instead of iteration splitting.
Node *exit = loop->is_loop_exit(iff);
if (!exit) continue;
int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
// Get boolean condition to test
Node *i1 = iff->in(1);
if (!i1->is_Bool()) continue;
BoolNode *bol = i1->as_Bool();
BoolTest b_test = bol->_test;
// Flip sense of test if exit condition is flipped
if (flip) {
b_test = b_test.negate();
}
// Get compare
Node *cmp = bol->in(1);
// Look for trip_counter + offset vs limit
Node *rc_exp = cmp->in(1);
Node *limit = cmp->in(2);
int scale_con= 1; // Assume trip counter not scaled
Node* limit_ctrl = get_ctrl(limit);
if (loop->is_member(get_loop(limit_ctrl))) {
// Compare might have operands swapped; commute them
b_test = b_test.commute();
rc_exp = cmp->in(2);
limit = cmp->in(1);
limit_ctrl = get_ctrl(limit);
if (loop->is_member(get_loop(limit_ctrl))) {
continue; // Both inputs are loop varying; cannot RCE
}
}
// Here we know 'limit' is loop invariant
// 'limit' maybe pinned below the zero trip test (probably from a
// previous round of rce), in which case, it can't be used in the
// zero trip test expression which must occur before the zero test's if.
if (is_dominator(ctrl, limit_ctrl)) {
continue; // Don't rce this check but continue looking for other candidates.
}
assert(is_dominator(compute_early_ctrl(limit, limit_ctrl), pre_end), "node pinned on loop exit test?");
// Check for scaled induction variable plus an offset
Node *offset = nullptr;
if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
continue;
}
Node* offset_ctrl = get_ctrl(offset);
if (loop->is_member(get_loop(offset_ctrl))) {
continue; // Offset is not really loop invariant
}
// Here we know 'offset' is loop invariant.
// As above for the 'limit', the 'offset' maybe pinned below the
// zero trip test.
if (is_dominator(ctrl, offset_ctrl)) {
continue; // Don't rce this check but continue looking for other candidates.
}
// offset and limit can have control set below the pre loop when they are not loop invariant in the pre loop.
// Update their control (and the control of inputs as needed) to be above pre_end
offset_ctrl = ensure_node_and_inputs_are_above_pre_end(pre_end, offset);
limit_ctrl = ensure_node_and_inputs_are_above_pre_end(pre_end, limit);
// offset and limit could have control below new_limit_ctrl if they are not loop invariant in the pre loop.
Node* next_limit_ctrl = dominated_node(new_limit_ctrl, offset_ctrl, limit_ctrl);
#ifdef ASSERT
if (TraceRangeLimitCheck) {
tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
bol->dump(2);
}
#endif
// At this point we have the expression as:
// scale_con * trip_counter + offset :: limit
// where scale_con, offset and limit are loop invariant. Trip_counter
// monotonically increases by stride_con, a constant. Both (or either)
// stride_con and scale_con can be negative which will flip about the
// sense of the test.
C->print_method(PHASE_BEFORE_RANGE_CHECK_ELIMINATION, 4, iff);
// Perform the limit computations in jlong to avoid overflow
jlong lscale_con = scale_con;
Node* int_offset = offset;
offset = new ConvI2LNode(offset);
register_new_node(offset, next_limit_ctrl);
Node* int_limit = limit;
limit = new ConvI2LNode(limit);
register_new_node(limit, next_limit_ctrl);
// Adjust pre and main loop limits to guard the correct iteration set
if (cmp->Opcode() == Op_CmpU) { // Unsigned compare is really 2 tests
if (b_test._test == BoolTest::lt) { // Range checks always use lt
// The underflow and overflow limits: 0 <= scale*I+offset < limit
add_constraint(stride_con, lscale_con, offset, zero, limit, next_limit_ctrl, &pre_limit, &main_limit);
Node* init = cl->uncasted_init_trip(true);
Node* opaque_init = new OpaqueLoopInitNode(C, init);
register_new_node(opaque_init, loop_entry);
InitializedAssertionPredicateCreator initialized_assertion_predicate_creator(this);
if (abs_stride_is_one) {
// If the main loop becomes empty and the array access for this range check is sunk out of the loop, the index
// for the array access will be set to the index value of the final iteration which could be out of loop.
// Add an Initialized Assertion Predicate for that corner case. The final iv is computed from LoopLimit which
// is the LoopNode::limit() only if abs(stride) == 1 otherwise the computation depends on LoopNode::init_trip()
// as well. When LoopLimit only depends on LoopNode::limit(), there are cases where the zero trip guard for
// the main loop doesn't constant fold after range check elimination but, the array access for the final
// iteration of the main loop is out of bound and the index for that access is out of range for the range
// check CastII.
// Note that we do not need to emit a Template Assertion Predicate to update this predicate. When further
// splitting this loop, the final IV will still be the same. When unrolling the loop, we will remove a
// previously added Initialized Assertion Predicate here. But then abs(stride) is greater than 1, and we
// cannot remove an empty loop with a constant limit when init is not a constant as well. We will use
// a LoopLimitCheck node that can only be folded if the zero grip guard is also foldable.
loop_entry = initialized_assertion_predicate_creator.create(final_iv_placeholder, loop_entry, stride_con,
scale_con, int_offset, int_limit,
AssertionPredicateType::FinalIv);
}
// Add two Template Assertion Predicates to create new Initialized Assertion Predicates from when either
// unrolling or splitting this main-loop further.
TemplateAssertionPredicateCreator template_assertion_predicate_creator(cl, scale_con , int_offset, int_limit,
this);
loop_entry = template_assertion_predicate_creator.create(loop_entry);
// Initialized Assertion Predicate for the value of the initial main-loop.
loop_entry = initialized_assertion_predicate_creator.create(init, loop_entry, stride_con, scale_con,
int_offset, int_limit,
AssertionPredicateType::InitValue);
} else {
if (PrintOpto) {
tty->print_cr("missed RCE opportunity");
}
continue; // In release mode, ignore it
}
} else { // Otherwise work on normal compares
switch(b_test._test) {
case BoolTest::gt:
// Fall into GE case
case BoolTest::ge:
// Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
lscale_con = -lscale_con;
offset = new SubLNode(zero, offset);
register_new_node(offset, next_limit_ctrl);
limit = new SubLNode(zero, limit);
register_new_node(limit, next_limit_ctrl);
// Fall into LE case
case BoolTest::le:
if (b_test._test != BoolTest::gt) {
// Convert X <= Y to X < Y+1
limit = new AddLNode(limit, one);
register_new_node(limit, next_limit_ctrl);
}
// Fall into LT case
case BoolTest::lt:
// The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
// Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
// to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
add_constraint(stride_con, lscale_con, offset, mini, limit, next_limit_ctrl, &pre_limit, &main_limit);
break;
default:
if (PrintOpto) {
tty->print_cr("missed RCE opportunity");
}
continue; // Unhandled case
}
}
// Only update variable tracking control for new nodes if it's indeed a range check that can be eliminated (and
// limits are updated)
new_limit_ctrl = next_limit_ctrl;
// Kill the eliminated test
C->set_major_progress();
Node* kill_con = intcon(1-flip);
_igvn.replace_input_of(iff, 1, kill_con);
// Find surviving projection
assert(iff->is_If(), "");
ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
// Find loads off the surviving projection; remove their control edge
for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
Node* cd = dp->fast_out(i); // Control-dependent node
if (cd->is_Load() && cd->depends_only_on_test()) { // Loads can now float around in the loop
// Allow the load to float around in the loop, or before it
// but NOT before the pre-loop.
_igvn.replace_input_of(cd, 0, ctrl); // ctrl, not null
--i;
--imax;
}
}
} // End of is IF
}
if (loop_entry != cl->skip_strip_mined()->in(LoopNode::EntryControl)) {
_igvn.replace_input_of(cl->skip_strip_mined(), LoopNode::EntryControl, loop_entry);
set_idom(cl->skip_strip_mined(), loop_entry, dom_depth(cl->skip_strip_mined()));
}
// Update loop limits
if (pre_limit != orig_limit) {
// Computed pre-loop limit can be outside of loop iterations range.
pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit)
: (Node*)new MaxINode(pre_limit, orig_limit);
register_new_node(pre_limit, new_limit_ctrl);
}
// new pre_limit can push Bool/Cmp/Opaque nodes down (when one of the eliminated condition has parameters that are not
// loop invariant in the pre loop.
set_ctrl(pre_opaq, new_limit_ctrl);
// Can't use new_limit_ctrl for Bool/Cmp because it can be out of loop while they are loop variant. Conservatively set
// control to latest possible one.
set_ctrl(pre_end->cmp_node(), pre_end->in(0));
set_ctrl(pre_end->in(1), pre_end->in(0));
_igvn.replace_input_of(pre_opaq, 1, pre_limit);
// Note:: we are making the main loop limit no longer precise;
// need to round up based on stride.
cl->set_nonexact_trip_count();
Node *main_cle = cl->loopexit();
Node *main_bol = main_cle->in(1);
// Hacking loop bounds; need private copies of exit test
if (main_bol->outcnt() > 1) { // BoolNode shared?
main_bol = main_bol->clone(); // Clone a private BoolNode
register_new_node(main_bol, main_cle->in(0));
_igvn.replace_input_of(main_cle, 1, main_bol);
}
Node *main_cmp = main_bol->in(1);
if (main_cmp->outcnt() > 1) { // CmpNode shared?
main_cmp = main_cmp->clone(); // Clone a private CmpNode
register_new_node(main_cmp, main_cle->in(0));
_igvn.replace_input_of(main_bol, 1, main_cmp);
}
assert(main_limit == cl->limit() || get_ctrl(main_limit) == new_limit_ctrl, "wrong control for added limit");
const TypeInt* orig_limit_t = _igvn.type(orig_limit)->is_int();
bool upward = cl->stride_con() > 0;
// The new loop limit is <= (for an upward loop) >= (for a downward loop) than the orig limit.
// The expression that computes the new limit may be too complicated and the computed type of the new limit
// may be too pessimistic. A CastII here guarantees it's not lost.
main_limit = new CastIINode(pre_ctrl, main_limit, TypeInt::make(upward ? min_jint : orig_limit_t->_lo,
upward ? orig_limit_t->_hi : max_jint, Type::WidenMax));
register_new_node(main_limit, new_limit_ctrl);
// Hack the now-private loop bounds
_igvn.replace_input_of(main_cmp, 2, main_limit);
if (abs_stride_is_one) {
Node* final_iv = new SubINode(main_limit, cl->stride());
register_new_node(final_iv, loop_entry);
_igvn.replace_node(final_iv_placeholder, final_iv);
}
// The OpaqueNode is unshared by design
assert(opqzm->outcnt() == 1, "cannot hack shared node");
_igvn.replace_input_of(opqzm, 1, main_limit);
// new main_limit can push opaque node for zero trip guard down (when one of the eliminated condition has parameters
// that are not loop invariant in the pre loop).
set_ctrl(opqzm, new_limit_ctrl);
// Bool/Cmp nodes for zero trip guard should have been assigned control between the main and pre loop (because zero
// trip guard depends on induction variable value out of pre loop) so shouldn't need to be adjusted
assert(is_dominator(new_limit_ctrl, get_ctrl(iffm->in(1)->in(1))), "control of cmp should be below control of updated input");
C->print_method(PHASE_AFTER_RANGE_CHECK_ELIMINATION, 4, cl);
}
// Adjust control for node and its inputs (and inputs of its inputs) to be above the pre end
Node* PhaseIdealLoop::ensure_node_and_inputs_are_above_pre_end(CountedLoopEndNode* pre_end, Node* node) {
Node* control = get_ctrl(node);
assert(is_dominator(compute_early_ctrl(node, control), pre_end), "node pinned on loop exit test?");
if (is_dominator(control, pre_end)) {
return control;
}
control = pre_end->in(0);
ResourceMark rm;
Unique_Node_List wq;
wq.push(node);
for (uint i = 0; i < wq.size(); i++) {
Node* n = wq.at(i);
assert(is_dominator(compute_early_ctrl(n, get_ctrl(n)), pre_end), "node pinned on loop exit test?");
set_ctrl(n, control);
for (uint j = 0; j < n->req(); j++) {
Node* in = n->in(j);
if (in != nullptr && has_ctrl(in) && !is_dominator(get_ctrl(in), pre_end)) {
wq.push(in);
}
}
}
return control;
}
bool IdealLoopTree::compute_has_range_checks() const {
assert(_head->is_CountedLoop(), "");
for (uint i = 0; i < _body.size(); i++) {
Node *iff = _body[i];
int iff_opc = iff->Opcode();
if (iff_opc == Op_If || iff_opc == Op_RangeCheck) {
return true;
}
}
return false;
}
//------------------------------DCE_loop_body----------------------------------
// Remove simplistic dead code from loop body
void IdealLoopTree::DCE_loop_body() {
for (uint i = 0; i < _body.size(); i++) {
if (_body.at(i)->outcnt() == 0) {
_body.map(i, _body.pop());
i--; // Ensure we revisit the updated index.
}
}
}
//------------------------------adjust_loop_exit_prob--------------------------
// Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
// Replace with a 1-in-10 exit guess.
void IdealLoopTree::adjust_loop_exit_prob(PhaseIdealLoop *phase) {
Node *test = tail();
while (test != _head) {
uint top = test->Opcode();
if (top == Op_IfTrue || top == Op_IfFalse) {
int test_con = ((ProjNode*)test)->_con;
assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
IfNode *iff = test->in(0)->as_If();
if (iff->outcnt() == 2) { // Ignore dead tests
Node *bol = iff->in(1);
if (bol && bol->req() > 1 && bol->in(1) &&
((bol->in(1)->Opcode() == Op_CompareAndExchangeB) ||
(bol->in(1)->Opcode() == Op_CompareAndExchangeS) ||
(bol->in(1)->Opcode() == Op_CompareAndExchangeI) ||
(bol->in(1)->Opcode() == Op_CompareAndExchangeL) ||
(bol->in(1)->Opcode() == Op_CompareAndExchangeP) ||
(bol->in(1)->Opcode() == Op_CompareAndExchangeN) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapB) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapS) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapI) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapL) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapP) ||
(bol->in(1)->Opcode() == Op_WeakCompareAndSwapN) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapB) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapS) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapI) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapL) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapP) ||
(bol->in(1)->Opcode() == Op_CompareAndSwapN) ||
(bol->in(1)->Opcode() == Op_ShenandoahCompareAndExchangeP) ||
(bol->in(1)->Opcode() == Op_ShenandoahCompareAndExchangeN) ||
(bol->in(1)->Opcode() == Op_ShenandoahWeakCompareAndSwapP) ||
(bol->in(1)->Opcode() == Op_ShenandoahWeakCompareAndSwapN) ||
(bol->in(1)->Opcode() == Op_ShenandoahCompareAndSwapP) ||
(bol->in(1)->Opcode() == Op_ShenandoahCompareAndSwapN)))
return; // Allocation loops RARELY take backedge
// Find the OTHER exit path from the IF
Node* ex = iff->proj_out(1-test_con);
float p = iff->_prob;
if (!phase->is_member(this, ex) && iff->_fcnt == COUNT_UNKNOWN) {
if (top == Op_IfTrue) {
if (p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
iff->_prob = PROB_STATIC_FREQUENT;
}
} else {
if (p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
iff->_prob = PROB_STATIC_INFREQUENT;
}
}
}
}
}
test = phase->idom(test);
}
}
static CountedLoopNode* locate_pre_from_main(CountedLoopNode* main_loop) {
assert(!main_loop->is_main_no_pre_loop(), "Does not have a pre loop");
Node* ctrl = main_loop->skip_assertion_predicates_with_halt();
assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
Node* iffm = ctrl->in(0);
assert(iffm->Opcode() == Op_If, "");
Node* p_f = iffm->in(0);
assert(p_f->Opcode() == Op_IfFalse, "");
CountedLoopNode* pre_loop = p_f->in(0)->as_CountedLoopEnd()->loopnode();
assert(pre_loop->is_pre_loop(), "No pre loop found");
return pre_loop;
}
// Remove the main and post loops and make the pre loop execute all
// iterations. Useful when the pre loop is found empty.
void IdealLoopTree::remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase) {
CountedLoopEndNode* pre_end = cl->loopexit();
Node* pre_cmp = pre_end->cmp_node();
if (pre_cmp->in(2)->Opcode() != Op_Opaque1) {
// Only safe to remove the main loop if the compiler optimized it
// out based on an unknown number of iterations
return;
}
// Can we find the main loop?
if (_next == nullptr) {
return;
}
Node* next_head = _next->_head;
if (!next_head->is_CountedLoop()) {
return;
}
CountedLoopNode* main_head = next_head->as_CountedLoop();
if (!main_head->is_main_loop() || main_head->is_main_no_pre_loop()) {
return;
}
// We found a main-loop after this pre-loop, but they might not belong together.
if (locate_pre_from_main(main_head) != cl) {
return;
}
Node* main_iff = main_head->skip_assertion_predicates_with_halt()->in(0);
// Remove the Opaque1Node of the pre loop and make it execute all iterations
phase->_igvn.replace_input_of(pre_cmp, 2, pre_cmp->in(2)->in(2));
// Remove the OpaqueZeroTripGuardNode of the main loop so it can be optimized out
Node* main_cmp = main_iff->in(1)->in(1);
assert(main_cmp->in(2)->Opcode() == Op_OpaqueZeroTripGuard, "main loop has no opaque node?");
phase->_igvn.replace_input_of(main_cmp, 2, main_cmp->in(2)->in(1));
}
//------------------------------do_remove_empty_loop---------------------------
// We always attempt remove empty loops. The approach is to replace the trip
// counter with the value it will have on the last iteration. This will break
// the loop.
bool IdealLoopTree::do_remove_empty_loop(PhaseIdealLoop *phase) {
if (!_head->is_CountedLoop()) {
return false; // Dead loop
}
if (!empty_loop_candidate(phase)) {
return false;
}
CountedLoopNode *cl = _head->as_CountedLoop();
#ifdef ASSERT
// Call collect_loop_core_nodes to exercise the assert that checks that it finds the right number of nodes
if (empty_loop_with_extra_nodes_candidate(phase)) {
Unique_Node_List wq;
collect_loop_core_nodes(phase, wq);
}
#endif
// Minimum size must be empty loop
if (_body.size() > EMPTY_LOOP_SIZE) {
// This loop has more nodes than an empty loop but, maybe they are only kept alive by the outer strip mined loop's
// safepoint. If they go away once the safepoint is removed, that loop is empty.
if (!empty_loop_with_data_nodes(phase)) {
return false;
}
}
if (cl->is_pre_loop()) {
// If the loop we are removing is a pre-loop then the main and post loop
// can be removed as well.
remove_main_post_loops(cl, phase);
}
#ifdef ASSERT
// Ensure at most one used phi exists, which is the iv.
Node* iv = nullptr;
for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
Node* n = cl->fast_out(i);
if ((n->Opcode() == Op_Phi) && (n->outcnt() > 0)) {
assert(iv == nullptr, "Too many phis");
iv = n;
}
}
assert(iv == cl->phi(), "Wrong phi");
#endif
// main and post loops have explicitly created zero trip guard
bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
if (needs_guard) {
// Skip guard if values not overlap.
const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
int stride_con = cl->stride_con();
if (stride_con > 0) {
needs_guard = (init_t->_hi >= limit_t->_lo);
} else {
needs_guard = (init_t->_lo <= limit_t->_hi);
}
}
if (needs_guard) {
// Check for an obvious zero trip guard.
Predicates predicates(cl->skip_strip_mined()->in(LoopNode::EntryControl));
Node* in_ctrl = predicates.entry();
if (in_ctrl->Opcode() == Op_IfTrue || in_ctrl->Opcode() == Op_IfFalse) {
bool maybe_swapped = (in_ctrl->Opcode() == Op_IfFalse);
// The test should look like just the backedge of a CountedLoop
Node* iff = in_ctrl->in(0);
if (iff->is_If()) {
Node* bol = iff->in(1);
if (bol->is_Bool()) {
BoolTest test = bol->as_Bool()->_test;
if (maybe_swapped) {
test._test = test.commute();
test._test = test.negate();
}
if (test._test == cl->loopexit()->test_trip()) {
Node* cmp = bol->in(1);
int init_idx = maybe_swapped ? 2 : 1;
int limit_idx = maybe_swapped ? 1 : 2;
if (cmp->is_Cmp() && cmp->in(init_idx) == cl->init_trip() && cmp->in(limit_idx) == cl->limit()) {
needs_guard = false;
}
}
}
}
}
}
#ifndef PRODUCT
if (PrintOpto) {
tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
this->dump_head();
} else if (TraceLoopOpts) {
tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
this->dump_head();
}
#endif
if (needs_guard) {
// Peel the loop to ensure there's a zero trip guard
Node_List old_new;
phase->do_peeling(this, old_new);
}
// Replace the phi at loop head with the final value of the last
// iteration (exact_limit - stride), to make sure the loop exit value
// is correct, for any users after the loop.
// Note: the final value after increment should not overflow since
// counted loop has limit check predicate.
Node* phi = cl->phi();
Node* exact_limit = phase->exact_limit(this);
// We need to pin the exact limit to prevent it from floating above the zero trip guard.
Node* cast_ii = ConstraintCastNode::make_cast_for_basic_type(
cl->in(LoopNode::EntryControl), exact_limit,
phase->_igvn.type(exact_limit),
ConstraintCastNode::UnconditionalDependency, T_INT);
phase->register_new_node(cast_ii, cl->in(LoopNode::EntryControl));
Node* final_iv = new SubINode(cast_ii, cl->stride());
phase->register_new_node(final_iv, cl->in(LoopNode::EntryControl));
phase->_igvn.replace_node(phi, final_iv);
// Set loop-exit condition to false. Then the CountedLoopEnd will collapse,
// because the back edge is never taken.
Node* zero = phase->_igvn.intcon(0);
phase->_igvn.replace_input_of(cl->loopexit(), CountedLoopEndNode::TestValue, zero);
phase->C->set_major_progress();
return true;
}
bool IdealLoopTree::empty_loop_candidate(PhaseIdealLoop* phase) const {
CountedLoopNode *cl = _head->as_CountedLoop();
if (!cl->is_valid_counted_loop(T_INT)) {
return false; // Malformed loop
}
if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) {
return false; // Infinite loop
}
return true;
}
bool IdealLoopTree::empty_loop_with_data_nodes(PhaseIdealLoop* phase) const {
CountedLoopNode* cl = _head->as_CountedLoop();
if (!cl->is_strip_mined() || !empty_loop_with_extra_nodes_candidate(phase)) {
return false;
}
Unique_Node_List empty_loop_nodes;
Unique_Node_List wq;
// Start from all data nodes in the loop body that are not one of the EMPTY_LOOP_SIZE nodes expected in an empty body
enqueue_data_nodes(phase, empty_loop_nodes, wq);
// and now follow uses
for (uint i = 0; i < wq.size(); ++i) {
Node* n = wq.at(i);
for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
Node* u = n->fast_out(j);
if (u->Opcode() == Op_SafePoint) {
// found a safepoint. Maybe this loop's safepoint or another loop safepoint.
if (!process_safepoint(phase, empty_loop_nodes, wq, u)) {
return false;
}
} else {
const Type* u_t = phase->_igvn.type(u);
if (u_t == Type::CONTROL || u_t == Type::MEMORY || u_t == Type::ABIO) {
// found a side effect
return false;
}
wq.push(u);
}
}
}
// Nodes (ignoring the EMPTY_LOOP_SIZE nodes of the "core" of the loop) are kept alive by otherwise empty loops'
// safepoints: kill them.
for (uint i = 0; i < wq.size(); ++i) {
Node* n = wq.at(i);
phase->_igvn.replace_node(n, phase->C->top());
}
#ifdef ASSERT
for (uint i = 0; i < _body.size(); ++i) {
Node* n = _body.at(i);
assert(wq.member(n) || empty_loop_nodes.member(n), "missed a node in the body?");
}
#endif
return true;
}
bool IdealLoopTree::process_safepoint(PhaseIdealLoop* phase, Unique_Node_List& empty_loop_nodes, Unique_Node_List& wq,
Node* sfpt) const {
CountedLoopNode* cl = _head->as_CountedLoop();
if (cl->outer_safepoint() == sfpt) {
// the current loop's safepoint
return true;
}
// Some other loop's safepoint. Maybe that loop is empty too.
IdealLoopTree* sfpt_loop = phase->get_loop(sfpt);
if (!sfpt_loop->_head->is_OuterStripMinedLoop()) {
return false;
}
IdealLoopTree* sfpt_inner_loop = sfpt_loop->_child;
CountedLoopNode* sfpt_cl = sfpt_inner_loop->_head->as_CountedLoop();
assert(sfpt_cl->is_strip_mined(), "inconsistent");
if (empty_loop_nodes.member(sfpt_cl)) {
// already taken care of
return true;
}
if (!sfpt_inner_loop->empty_loop_candidate(phase) || !sfpt_inner_loop->empty_loop_with_extra_nodes_candidate(phase)) {
return false;
}
// Enqueue the nodes of that loop for processing too
sfpt_inner_loop->enqueue_data_nodes(phase, empty_loop_nodes, wq);
return true;
}
bool IdealLoopTree::empty_loop_with_extra_nodes_candidate(PhaseIdealLoop* phase) const {
CountedLoopNode *cl = _head->as_CountedLoop();
// No other control flow node in the loop body
if (cl->loopexit()->in(0) != cl) {
return false;
}
if (phase->is_member(this, phase->get_ctrl(cl->limit()))) {
return false;
}
return true;
}
void IdealLoopTree::enqueue_data_nodes(PhaseIdealLoop* phase, Unique_Node_List& empty_loop_nodes,
Unique_Node_List& wq) const {
collect_loop_core_nodes(phase, empty_loop_nodes);
for (uint i = 0; i < _body.size(); ++i) {
Node* n = _body.at(i);
if (!empty_loop_nodes.member(n)) {
wq.push(n);
}
}
}
// This collects the node that would be left if this body was empty
void IdealLoopTree::collect_loop_core_nodes(PhaseIdealLoop* phase, Unique_Node_List& wq) const {
uint before = wq.size();
wq.push(_head->in(LoopNode::LoopBackControl));
for (uint i = before; i < wq.size(); ++i) {
Node* n = wq.at(i);
for (uint j = 0; j < n->req(); ++j) {
Node* in = n->in(j);
if (in != nullptr) {
if (phase->get_loop(phase->ctrl_or_self(in)) == this) {
wq.push(in);
}
}
}
}
assert(wq.size() - before == EMPTY_LOOP_SIZE, "expect the EMPTY_LOOP_SIZE nodes of this body if empty");
}
//------------------------------do_one_iteration_loop--------------------------
// Convert one iteration loop into normal code.
bool IdealLoopTree::do_one_iteration_loop(PhaseIdealLoop *phase) {
if (!_head->as_Loop()->is_valid_counted_loop(T_INT)) {
return false; // Only for counted loop
}
CountedLoopNode *cl = _head->as_CountedLoop();
if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
return false;
}
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("OneIteration ");
this->dump_head();
}
#endif
Node *init_n = cl->init_trip();
// Loop boundaries should be constant since trip count is exact.
assert((cl->stride_con() > 0 && init_n->get_int() + cl->stride_con() >= cl->limit()->get_int()) ||
(cl->stride_con() < 0 && init_n->get_int() + cl->stride_con() <= cl->limit()->get_int()), "should be one iteration");
// Replace the phi at loop head with the value of the init_trip.
// Then the CountedLoopEnd will collapse (backedge will not be taken)
// and all loop-invariant uses of the exit values will be correct.
phase->_igvn.replace_node(cl->phi(), cl->init_trip());
phase->C->set_major_progress();
return true;
}
//=============================================================================
//------------------------------iteration_split_impl---------------------------
bool IdealLoopTree::iteration_split_impl(PhaseIdealLoop *phase, Node_List &old_new) {
if (!_head->is_Loop()) {
// Head could be a region with a NeverBranch that was added in beautify loops but the region was not
// yet transformed into a LoopNode. Bail out and wait until beautify loops turns it into a Loop node.
return false;
}
// Compute loop trip count if possible.
compute_trip_count(phase);
// Convert one iteration loop into normal code.
if (do_one_iteration_loop(phase)) {
return true;
}
// Check and remove empty loops (spam micro-benchmarks)
if (do_remove_empty_loop(phase)) {
return true; // Here we removed an empty loop
}
AutoNodeBudget node_budget(phase);
// Non-counted loops may be peeled; exactly 1 iteration is peeled.
// This removes loop-invariant tests (usually null checks).
if (!_head->is_CountedLoop()) { // Non-counted loop
if (PartialPeelLoop) {
bool rc = phase->partial_peel(this, old_new);
if (Compile::current()->failing()) { return false; }
if (rc) {
// Partial peel succeeded so terminate this round of loop opts
return false;
}
}
if (policy_peeling(phase)) { // Should we peel?
if (PrintOpto) { tty->print_cr("should_peel"); }
phase->do_peeling(this, old_new);
} else if (policy_unswitching(phase)) {
phase->do_unswitching(this, old_new);
return false; // need to recalculate idom data
} else if (phase->duplicate_loop_backedge(this, old_new)) {
return false;
} else if (_head->is_LongCountedLoop()) {
phase->create_loop_nest(this, old_new);
}
return true;
}
CountedLoopNode *cl = _head->as_CountedLoop();
if (!cl->is_valid_counted_loop(T_INT)) return true; // Ignore various kinds of broken loops
// Do nothing special to pre- and post- loops
if (cl->is_pre_loop() || cl->is_post_loop()) return true;
// With multiversioning, we create a fast_loop and a slow_loop, and a multiversion_if that
// decides which loop is taken at runtime. At first, the multiversion_if always takes the
// fast_loop, and we only optimize the fast_loop. Since we are not sure if we will ever use
// the slow_loop, we delay optimizations for it, so we do not waste compile time and code
// size. If we never change the condition of the multiversion_if, the slow_loop is eventually
// folded away after loop-opts. While optimizing the fast_loop, we may want to perform some
// speculative optimization, for which we need a runtime-check. We add this runtime-check
// condition to the multiversion_if. Now, it becomes possible to execute the slow_loop at
// runtime, and we resume optimizations for slow_loop ("un-delay" it).
// TLDR: If the slow_loop is still in "delay" mode, check if the multiversion_if was changed
// and we should now resume optimizations for it.
if (cl->is_multiversion_delayed_slow_loop() &&
!phase->try_resume_optimizations_for_delayed_slow_loop(this)) {
// We are still delayed, so wait with further loop-opts.
return true;
}
// Compute loop trip count from profile data
compute_profile_trip_cnt(phase);
// Before attempting fancy unrolling, RCE or alignment, see if we want
// to completely unroll this loop or do loop unswitching.
if (cl->is_normal_loop()) {
if (policy_unswitching(phase)) {
phase->do_unswitching(this, old_new);
return false; // need to recalculate idom data
}
if (policy_maximally_unroll(phase)) {
// Here we did some unrolling and peeling. Eventually we will
// completely unroll this loop and it will no longer be a loop.
phase->do_maximally_unroll(this, old_new);
return true;
}
if (StressDuplicateBackedge && phase->duplicate_loop_backedge(this, old_new)) {
return false;
}
}
uint est_peeling = estimate_peeling(phase);
bool should_peel = 0 < est_peeling;
// Counted loops may be peeled, or may need some iterations run up
// front for RCE. Thus we clone a full loop up front whose trip count is
// at least 1 (if peeling), but may be several more.
// The main loop will start cache-line aligned with at least 1
// iteration of the unrolled body (zero-trip test required) and
// will have some range checks removed.
// A post-loop will finish any odd iterations (leftover after
// unrolling), plus any needed for RCE purposes.
bool should_unroll = policy_unroll(phase);
bool should_rce = policy_range_check(phase, false, T_INT);
bool should_rce_long = policy_range_check(phase, false, T_LONG);
// If not RCE'ing (iteration splitting), then we do not need a pre-loop.
// We may still need to peel an initial iteration but we will not
// be needing an unknown number of pre-iterations.
//
// Basically, if peel_only reports TRUE first time through, we will not
// be able to later do RCE on this loop.
bool peel_only = policy_peel_only(phase) && !should_rce;
// If we have any of these conditions (RCE, unrolling) met, then
// we switch to the pre-/main-/post-loop model. This model also covers
// peeling.
if (should_rce || should_unroll) {
if (cl->is_normal_loop()) { // Convert to 'pre/main/post' loops
if (should_rce_long && phase->create_loop_nest(this, old_new)) {
return true;
}
uint estimate = est_loop_clone_sz(3);
if (!phase->may_require_nodes(estimate)) {
return false;
}
if (!peel_only) {
// We are going to add pre-loop and post-loop (PreMainPost).
// But should we also multiversion for auto-vectorization speculative
// checks, i.e. fast and slow-paths?
// Note: Just PeelMainPost is not sufficient, as we could never find the
// multiversion_if again from the main loop: we need a nicely structured
// pre-loop, a peeled iteration cannot easily be parsed through.
phase->maybe_multiversion_for_auto_vectorization_runtime_checks(this, old_new);
}
phase->insert_pre_post_loops(this, old_new, peel_only);
}
// Adjust the pre- and main-loop limits to let the pre and post loops run
// with full checks, but the main-loop with no checks. Remove said checks
// from the main body.
if (should_rce) {
phase->do_range_check(this);
}
// Double loop body for unrolling. Adjust the minimum-trip test (will do
// twice as many iterations as before) and the main body limit (only do
// an even number of trips). If we are peeling, we might enable some RCE
// and we'd rather unroll the post-RCE'd loop SO... do not unroll if
// peeling.
if (should_unroll && !should_peel) {
if (SuperWordLoopUnrollAnalysis) {
phase->insert_vector_post_loop(this, old_new);
}
phase->do_unroll(this, old_new, true);
}
} else { // Else we have an unchanged counted loop
if (should_peel) { // Might want to peel but do nothing else
if (phase->may_require_nodes(est_peeling)) {
phase->do_peeling(this, old_new);
}
}
if (should_rce_long) {
phase->create_loop_nest(this, old_new);
}
}
return true;
}
//=============================================================================
//------------------------------iteration_split--------------------------------
bool IdealLoopTree::iteration_split(PhaseIdealLoop* phase, Node_List &old_new) {
// Recursively iteration split nested loops
if (_child && !_child->iteration_split(phase, old_new)) {
return false;
}
// Clean out prior deadwood
DCE_loop_body();
// Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
// Replace with a 1-in-10 exit guess.
if (!is_root() && is_loop()) {
adjust_loop_exit_prob(phase);
}
// Unrolling, RCE and peeling efforts, iff innermost loop.
if (_allow_optimizations && is_innermost()) {
if (!_has_call) {
if (!iteration_split_impl(phase, old_new)) {
return false;
}
} else {
AutoNodeBudget node_budget(phase);
if (policy_unswitching(phase)) {
phase->do_unswitching(this, old_new);
return false; // need to recalculate idom data
}
}
}
if (_next && !_next->iteration_split(phase, old_new)) {
return false;
}
return true;
}
//=============================================================================
// Process all the loops in the loop tree and replace any fill
// patterns with an intrinsic version.
bool PhaseIdealLoop::do_intrinsify_fill() {
bool changed = false;
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
changed |= intrinsify_fill(lpt);
}
return changed;
}
// Examine an inner loop looking for a single store of an invariant
// value in a unit stride loop,
bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
Node*& shift, Node*& con) {
const char* msg = nullptr;
Node* msg_node = nullptr;
store_value = nullptr;
con = nullptr;
shift = nullptr;
// Process the loop looking for stores. If there are multiple
// stores or extra control flow give at this point.
CountedLoopNode* head = lpt->_head->as_CountedLoop();
for (uint i = 0; msg == nullptr && i < lpt->_body.size(); i++) {
Node* n = lpt->_body.at(i);
if (n->outcnt() == 0) continue; // Ignore dead
if (n->is_Store()) {
if (store != nullptr) {
msg = "multiple stores";
break;
}
int opc = n->Opcode();
if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass) {
msg = "oop fills not handled";
break;
}
Node* value = n->in(MemNode::ValueIn);
if (!lpt->is_invariant(value)) {
msg = "variant store value";
} else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
msg = "not array address";
}
store = n;
store_value = value;
} else if (n->is_If() && n != head->loopexit_or_null()) {
msg = "extra control flow";
msg_node = n;
}
}
if (store == nullptr) {
// No store in loop
return false;
}
if (msg == nullptr && store->as_Mem()->is_mismatched_access()) {
// This optimization does not currently support mismatched stores, where the
// type of the value to be stored differs from the element type of the
// destination array. Such patterns arise for example from memory segment
// initialization. This limitation could be overcome by extending this
// function's address matching logic and ensuring that the fill intrinsic
// implementations support mismatched array filling.
msg = "mismatched store";
}
if (msg == nullptr && head->stride_con() != 1) {
// could handle negative strides too
if (head->stride_con() < 0) {
msg = "negative stride";
} else {
msg = "non-unit stride";
}
}
if (msg == nullptr && !store->in(MemNode::Address)->is_AddP()) {
msg = "can't handle store address";
msg_node = store->in(MemNode::Address);
}
if (msg == nullptr &&
(!store->in(MemNode::Memory)->is_Phi() ||
store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
msg = "store memory isn't proper phi";
msg_node = store->in(MemNode::Memory);
}
// Make sure there is an appropriate fill routine
BasicType t = msg == nullptr ?
store->adr_type()->isa_aryptr()->elem()->array_element_basic_type() : T_VOID;
const char* fill_name;
if (msg == nullptr &&
StubRoutines::select_fill_function(t, false, fill_name) == nullptr) {
msg = "unsupported store";
msg_node = store;
}
if (msg != nullptr) {
#ifndef PRODUCT
if (TraceOptimizeFill) {
tty->print_cr("not fill intrinsic candidate: %s", msg);
if (msg_node != nullptr) msg_node->dump();
}
#endif
return false;
}
// Make sure the address expression can be handled. It should be
// head->phi * elsize + con. head->phi might have a ConvI2L(CastII()).
Node* elements[4];
Node* cast = nullptr;
Node* conv = nullptr;
bool found_index = false;
int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
for (int e = 0; e < count; e++) {
Node* n = elements[e];
if (n->is_Con() && con == nullptr) {
con = n;
} else if (n->Opcode() == Op_LShiftX && shift == nullptr) {
Node* value = n->in(1);
#ifdef _LP64
if (value->Opcode() == Op_ConvI2L) {
conv = value;
value = value->in(1);
}
if (value->Opcode() == Op_CastII &&
value->as_CastII()->has_range_check()) {
// Skip range check dependent CastII nodes
cast = value;
value = value->in(1);
}
#endif
if (value != head->phi()) {
msg = "unhandled shift in address";
} else {
if (type2aelembytes(t, true) != (1 << n->in(2)->get_int())) {
msg = "scale doesn't match";
} else {
found_index = true;
shift = n;
}
}
} else if (n->Opcode() == Op_ConvI2L && conv == nullptr) {
conv = n;
n = n->in(1);
if (n->Opcode() == Op_CastII &&
n->as_CastII()->has_range_check()) {
// Skip range check dependent CastII nodes
cast = n;
n = n->in(1);
}
if (n == head->phi()) {
found_index = true;
} else {
msg = "unhandled input to ConvI2L";
}
} else if (n == head->phi()) {
// no shift, check below for allowed cases
found_index = true;
} else {
msg = "unhandled node in address";
msg_node = n;
}
}
if (count == -1) {
msg = "malformed address expression";
msg_node = store;
}
if (!found_index) {
msg = "missing use of index";
}
// byte sized items won't have a shift
if (msg == nullptr && shift == nullptr && t != T_BYTE && t != T_BOOLEAN) {
msg = "can't find shift";
msg_node = store;
}
if (msg != nullptr) {
#ifndef PRODUCT
if (TraceOptimizeFill) {
tty->print_cr("not fill intrinsic: %s", msg);
if (msg_node != nullptr) msg_node->dump();
}
#endif
return false;
}
// No make sure all the other nodes in the loop can be handled
VectorSet ok;
// store related values are ok
ok.set(store->_idx);
ok.set(store->in(MemNode::Memory)->_idx);
CountedLoopEndNode* loop_exit = head->loopexit();
// Loop structure is ok
ok.set(head->_idx);
ok.set(loop_exit->_idx);
ok.set(head->phi()->_idx);
ok.set(head->incr()->_idx);
ok.set(loop_exit->cmp_node()->_idx);
ok.set(loop_exit->in(1)->_idx);
// Address elements are ok
if (con) ok.set(con->_idx);
if (shift) ok.set(shift->_idx);
if (cast) ok.set(cast->_idx);
if (conv) ok.set(conv->_idx);
for (uint i = 0; msg == nullptr && i < lpt->_body.size(); i++) {
Node* n = lpt->_body.at(i);
if (n->outcnt() == 0) continue; // Ignore dead
if (ok.test(n->_idx)) continue;
// Backedge projection is ok
if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
if (!n->is_AddP()) {
msg = "unhandled node";
msg_node = n;
break;
}
}
// Make sure no unexpected values are used outside the loop
for (uint i = 0; msg == nullptr && i < lpt->_body.size(); i++) {
Node* n = lpt->_body.at(i);
// These values can be replaced with other nodes if they are used
// outside the loop.
if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
Node* use = iter.get();
if (!lpt->_body.contains(use)) {
msg = "node is used outside loop";
msg_node = n;
break;
}
}
}
#ifdef ASSERT
if (TraceOptimizeFill) {
if (msg != nullptr) {
tty->print_cr("no fill intrinsic: %s", msg);
if (msg_node != nullptr) msg_node->dump();
} else {
tty->print_cr("fill intrinsic for:");
}
store->dump();
if (Verbose) {
lpt->_body.dump();
}
}
#endif
return msg == nullptr;
}
bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
// Only for counted inner loops
if (!lpt->is_counted() || !lpt->is_innermost()) {
return false;
}
// Must have constant stride
CountedLoopNode* head = lpt->_head->as_CountedLoop();
if (!head->is_valid_counted_loop(T_INT) || !head->is_normal_loop()) {
return false;
}
head->verify_strip_mined(1);
// Check that the body only contains a store of a loop invariant
// value that is indexed by the loop phi.
Node* store = nullptr;
Node* store_value = nullptr;
Node* shift = nullptr;
Node* offset = nullptr;
if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
return false;
}
Node* exit = head->loopexit()->proj_out_or_null(0);
if (exit == nullptr) {
return false;
}
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("ArrayFill ");
lpt->dump_head();
}
#endif
// Now replace the whole loop body by a call to a fill routine that
// covers the same region as the loop.
Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
// Build an expression for the beginning of the copy region
Node* index = head->init_trip();
#ifdef _LP64
index = new ConvI2LNode(index);
_igvn.register_new_node_with_optimizer(index);
#endif
if (shift != nullptr) {
// byte arrays don't require a shift but others do.
index = new LShiftXNode(index, shift->in(2));
_igvn.register_new_node_with_optimizer(index);
}
Node* from = new AddPNode(base, base, index);
_igvn.register_new_node_with_optimizer(from);
// For normal array fills, C2 uses two AddP nodes for array element
// addressing. But for array fills with Unsafe call, there's only one
// AddP node adding an absolute offset, so we do a null check here.
assert(offset != nullptr || C->has_unsafe_access(),
"Only array fills with unsafe have no extra offset");
if (offset != nullptr) {
from = new AddPNode(base, from, offset);
_igvn.register_new_node_with_optimizer(from);
}
// Compute the number of elements to copy
Node* len = new SubINode(head->limit(), head->init_trip());
_igvn.register_new_node_with_optimizer(len);
// If the store is on the backedge, it is not executed in the last
// iteration, and we must subtract 1 from the len.
Node* backedge = head->loopexit()->proj_out(1);
if (store->in(0) == backedge) {
len = new SubINode(len, _igvn.intcon(1));
_igvn.register_new_node_with_optimizer(len);
#ifndef PRODUCT
if (TraceOptimizeFill) {
tty->print_cr("ArrayFill store on backedge, subtract 1 from len.");
}
#endif
}
BasicType t = store->adr_type()->isa_aryptr()->elem()->array_element_basic_type();
bool aligned = false;
if (offset != nullptr && head->init_trip()->is_Con()) {
int element_size = type2aelembytes(t);
aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
}
// Build a call to the fill routine
const char* fill_name;
address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
assert(fill != nullptr, "what?");
// Convert float/double to int/long for fill routines
if (t == T_FLOAT) {
store_value = new MoveF2INode(store_value);
_igvn.register_new_node_with_optimizer(store_value);
} else if (t == T_DOUBLE) {
store_value = new MoveD2LNode(store_value);
_igvn.register_new_node_with_optimizer(store_value);
}
Node* mem_phi = store->in(MemNode::Memory);
Node* result_ctrl;
Node* result_mem;
const TypeFunc* call_type = OptoRuntime::array_fill_Type();
CallLeafNode *call = new CallLeafNoFPNode(call_type, fill,
fill_name, TypeAryPtr::get_array_body_type(t));
uint cnt = 0;
call->init_req(TypeFunc::Parms + cnt++, from);
call->init_req(TypeFunc::Parms + cnt++, store_value);
#ifdef _LP64
len = new ConvI2LNode(len);
_igvn.register_new_node_with_optimizer(len);
#endif
call->init_req(TypeFunc::Parms + cnt++, len);
#ifdef _LP64
call->init_req(TypeFunc::Parms + cnt++, C->top());
#endif
call->init_req(TypeFunc::Control, head->init_control());
call->init_req(TypeFunc::I_O, C->top()); // Does no I/O.
call->init_req(TypeFunc::Memory, mem_phi->in(LoopNode::EntryControl));
call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out_or_null(TypeFunc::ReturnAdr));
call->init_req(TypeFunc::FramePtr, C->start()->proj_out_or_null(TypeFunc::FramePtr));
_igvn.register_new_node_with_optimizer(call);
result_ctrl = new ProjNode(call,TypeFunc::Control);
_igvn.register_new_node_with_optimizer(result_ctrl);
result_mem = new ProjNode(call,TypeFunc::Memory);
_igvn.register_new_node_with_optimizer(result_mem);
/* Disable following optimization until proper fix (add missing checks).
// If this fill is tightly coupled to an allocation and overwrites
// the whole body, allow it to take over the zeroing.
AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
if (alloc != nullptr && alloc->is_AllocateArray()) {
Node* length = alloc->as_AllocateArray()->Ideal_length();
if (head->limit() == length &&
head->init_trip() == _igvn.intcon(0)) {
if (TraceOptimizeFill) {
tty->print_cr("Eliminated zeroing in allocation");
}
alloc->maybe_set_complete(&_igvn);
} else {
#ifdef ASSERT
if (TraceOptimizeFill) {
tty->print_cr("filling array but bounds don't match");
alloc->dump();
head->init_trip()->dump();
head->limit()->dump();
length->dump();
}
#endif
}
}
*/
if (head->is_strip_mined()) {
// Inner strip mined loop goes away so get rid of outer strip
// mined loop
Node* outer_sfpt = head->outer_safepoint();
Node* in = outer_sfpt->in(0);
Node* outer_out = head->outer_loop_exit();
lazy_replace(outer_out, in);
_igvn.replace_input_of(outer_sfpt, 0, C->top());
}
// Redirect the old control and memory edges that are outside the loop.
// Sometimes the memory phi of the head is used as the outgoing
// state of the loop. It's safe in this case to replace it with the
// result_mem.
_igvn.replace_node(store->in(MemNode::Memory), result_mem);
lazy_replace(exit, result_ctrl);
_igvn.replace_node(store, result_mem);
// Any uses the increment outside of the loop become the loop limit.
_igvn.replace_node(head->incr(), head->limit());
// Disconnect the head from the loop.
for (uint i = 0; i < lpt->_body.size(); i++) {
Node* n = lpt->_body.at(i);
_igvn.replace_node(n, C->top());
}
#ifndef PRODUCT
if (TraceOptimizeFill) {
tty->print("ArrayFill call ");
call->dump();
}
#endif
return true;
}