src/hotspot/cpu/riscv/vtableStubs_riscv.cpp

/*
 * Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2014, Red Hat Inc. All rights reserved.
 * Copyright (c) 2020, 2023, Huawei Technologies Co., Ltd. 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 "asm/assembler.inline.hpp"
#include "asm/macroAssembler.inline.hpp"
#include "code/compiledIC.hpp"
#include "code/vtableStubs.hpp"
#include "interp_masm_riscv.hpp"
#include "memory/resourceArea.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klassVtable.hpp"
#include "runtime/sharedRuntime.hpp"
#include "vmreg_riscv.inline.hpp"
#ifdef COMPILER2
#include "opto/runtime.hpp"
#endif

// machine-dependent part of VtableStubs: create VtableStub of correct size and
// initialize its code

#define __ masm->

#ifndef PRODUCT
extern "C" void bad_compiled_vtable_index(JavaThread* thread, oop receiver, int index);
#endif

VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
  // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
  const int stub_code_length = code_size_limit(true);
  VtableStub* s = new(stub_code_length) VtableStub(true, vtable_index);
  // Can be null if there is no free space in the code cache.
  if (s == nullptr) {
    return nullptr;
  }

  // Count unused bytes in instruction sequences of variable size.
  // We add them to the computed buffer size in order to avoid
  // overflow in subsequently generated stubs.
  address   start_pc = nullptr;
  int       slop_bytes = 0;
  int       slop_delta = 0;

  ResourceMark    rm;
  CodeBuffer      cb(s->entry_point(), stub_code_length);
  MacroAssembler* masm = new MacroAssembler(&cb);
  assert_cond(masm != nullptr);

#if (!defined(PRODUCT) && defined(COMPILER2))
  if (CountCompiledCalls) {
    __ la(t2, ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
    __ increment(Address(t2));
  }
#endif

  // get receiver (need to skip return address on top of stack)
  assert(VtableStub::receiver_location() == j_rarg0->as_VMReg(), "receiver expected in j_rarg0");

  // get receiver klass
  address npe_addr = __ pc();
  __ load_klass(t2, j_rarg0);

#ifndef PRODUCT
  if (DebugVtables) {
    Label L;
    start_pc = __ pc();

    // check offset vs vtable length
    __ lwu(t0, Address(t2, Klass::vtable_length_offset()));
    __ mv(t1, vtable_index * vtableEntry::size());
    __ bgt(t0, t1, L);
    __ enter();
    __ mv(x12, vtable_index);

    __ call_VM(noreg, CAST_FROM_FN_PTR(address, bad_compiled_vtable_index), j_rarg0, x12);
    const ptrdiff_t estimate = 256;
    const ptrdiff_t codesize = __ pc() - start_pc;
    slop_delta = estimate - codesize;  // call_VM varies in length, depending on data
    slop_bytes += slop_delta;
    assert(slop_delta >= 0, "vtable #%d: Code size estimate (%d) for DebugVtables too small, required: %d", vtable_index, (int)estimate, (int)codesize);

    __ leave();
    __ bind(L);
  }
#endif // PRODUCT

  start_pc = __ pc();
  __ lookup_virtual_method(t2, vtable_index, xmethod);
  // lookup_virtual_method generates
  // 4 instructions (maximum value encountered in normal case):li(lui + addiw) + add + ld
  // 1 instruction (best case):ld * 1
  slop_delta = 16 - (int)(__ pc() - start_pc);
  slop_bytes += slop_delta;
  assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);

#ifndef PRODUCT
  if (DebugVtables) {
    Label L;
    __ beqz(xmethod, L);
    __ ld(t0, Address(xmethod, Method::from_compiled_offset()));
    __ bnez(t0, L);
    __ stop("Vtable entry is null");
    __ bind(L);
  }
#endif // PRODUCT

  // x10: receiver klass
  // xmethod: Method*
  // x12: receiver
  address ame_addr = __ pc();
  __ ld(t1, Address(xmethod, Method::from_compiled_offset()));
  __ jr(t1);

  masm->flush();
  bookkeeping(masm, tty, s, npe_addr, ame_addr, true, vtable_index, slop_bytes, 0);

  return s;
}

VtableStub* VtableStubs::create_itable_stub(int itable_index) {
  // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
  const int stub_code_length = code_size_limit(false);
  VtableStub* s = new(stub_code_length) VtableStub(false, itable_index);
  // Can be null if there is no free space in the code cache.
  if (s == nullptr) {
    return nullptr;
  }
  // Count unused bytes in instruction sequences of variable size.
  // We add them to the computed buffer size in order to avoid
  // overflow in subsequently generated stubs.
  address   start_pc = nullptr;
  int       slop_bytes = 0;
  int       slop_delta = 0;

  ResourceMark    rm;
  CodeBuffer      cb(s->entry_point(), stub_code_length);
  MacroAssembler* masm = new MacroAssembler(&cb);
  assert_cond(masm != nullptr);

  // Real entry arguments:
  //  t0: CompiledICData
  //  j_rarg0: Receiver
  // Make sure the move of CompiledICData from t0 to t1 is the frist thing that happens.
  // Otherwise we risk clobber t0 as it is used as scratch.
  __ mv(t1, t0);

#if (!defined(PRODUCT) && defined(COMPILER2))
  if (CountCompiledCalls) {
    __ la(x18, ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
    __ increment(Address(x18));
  }
#endif

  // get receiver (need to skip return address on top of stack)
  assert(VtableStub::receiver_location() == j_rarg0->as_VMReg(), "receiver expected in j_rarg0");

  // Arguments from this point:
  //  t1 (moved from t0): CompiledICData
  //  j_rarg0: Receiver

  // This stub is called from compiled code which has no callee-saved registers,
  // so all registers except arguments are free at this point.
  const Register recv_klass_reg     = x18;
  const Register holder_klass_reg   = x19; // declaring interface klass (DEFC)
  const Register resolved_klass_reg = x30; // resolved interface klass (REFC)
  const Register temp_reg           = x28;
  const Register temp_reg2          = x29;
  const Register icdata_reg         = t1;

  Label L_no_such_interface;

  __ ld(resolved_klass_reg, Address(icdata_reg, CompiledICData::itable_refc_klass_offset()));
  __ ld(holder_klass_reg,   Address(icdata_reg, CompiledICData::itable_defc_klass_offset()));

  start_pc = __ pc();

  // get receiver klass (also an implicit null-check)
  address npe_addr = __ pc();
  __ load_klass(recv_klass_reg, j_rarg0);

  // Receiver subtype check against REFC.
  // Get selected method from declaring class and itable index
  __ lookup_interface_method_stub(recv_klass_reg, holder_klass_reg, resolved_klass_reg, xmethod,
                                  temp_reg, temp_reg2, itable_index, L_no_such_interface);

  // Reduce "estimate" such that "padding" does not drop below 8.
  const ptrdiff_t estimate = 256;
  const ptrdiff_t codesize = __ pc() - start_pc;
  slop_delta = (int)(estimate - codesize);
  slop_bytes += slop_delta;
  assert(slop_delta >= 0, "itable #%d: Code size estimate (%d) for lookup_interface_method too small, required: %d", itable_index, (int)estimate, (int)codesize);

#ifdef ASSERT
  if (DebugVtables) {
    Label L2;
    __ beqz(xmethod, L2);
    __ ld(t0, Address(xmethod, Method::from_compiled_offset()));
    __ bnez(t0, L2);
    __ stop("compiler entrypoint is null");
    __ bind(L2);
  }
#endif // ASSERT

  // xmethod: Method*
  // j_rarg0: receiver
  address ame_addr = __ pc();
  __ ld(t1, Address(xmethod, Method::from_compiled_offset()));
  __ jr(t1);

  __ bind(L_no_such_interface);
  // Handle IncompatibleClassChangeError in itable stubs.
  // More detailed error message.
  // We force resolving of the call site by jumping to the "handle
  // wrong method" stub, and so let the interpreter runtime do all the
  // dirty work.
  assert(SharedRuntime::get_handle_wrong_method_stub() != nullptr, "check initialization order");
  __ far_jump(RuntimeAddress(SharedRuntime::get_handle_wrong_method_stub()));

  masm->flush();
  bookkeeping(masm, tty, s, npe_addr, ame_addr, false, itable_index, slop_bytes, 0);

  return s;
}

int VtableStub::pd_code_alignment() {
  // RISCV cache line size is not an architected constant. We just align on word size.
  const unsigned int icache_line_size = wordSize;
  return icache_line_size;
}