src/hotspot/cpu/x86/c1_MacroAssembler_x86.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 *
 * 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.
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#include "c1/c1_MacroAssembler.hpp"
#include "c1/c1_Runtime1.hpp"
#include "code/compiledIC.hpp"
#include "compiler/compilerDefinitions.inline.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/barrierSetAssembler.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "interpreter/interpreter.hpp"
#include "oops/arrayOop.hpp"
#include "oops/markWord.hpp"
#include "runtime/basicLock.hpp"
#include "runtime/globals.hpp"
#include "runtime/os.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/stubRoutines.hpp"
#include "utilities/checkedCast.hpp"
#include "utilities/globalDefinitions.hpp"

int C1_MacroAssembler::lock_object(Register hdr, Register obj, Register disp_hdr, Register tmp, Label& slow_case) {
  const int aligned_mask = BytesPerWord -1;
  const int hdr_offset = oopDesc::mark_offset_in_bytes();
  assert(hdr == rax, "hdr must be rax, for the cmpxchg instruction");
  assert_different_registers(hdr, obj, disp_hdr, tmp);
  int null_check_offset = -1;

  verify_oop(obj);

  // save object being locked into the BasicObjectLock
  movptr(Address(disp_hdr, BasicObjectLock::obj_offset()), obj);

  null_check_offset = offset();

  if (LockingMode == LM_LIGHTWEIGHT) {
    lightweight_lock(disp_hdr, obj, hdr, tmp, slow_case);
  } else  if (LockingMode == LM_LEGACY) {
    Label done;

    if (DiagnoseSyncOnValueBasedClasses != 0) {
      load_klass(hdr, obj, rscratch1);
      testb(Address(hdr, Klass::misc_flags_offset()), KlassFlags::_misc_is_value_based_class);
      jcc(Assembler::notZero, slow_case);
    }

    // Load object header
    movptr(hdr, Address(obj, hdr_offset));
    // and mark it as unlocked
    orptr(hdr, markWord::unlocked_value);
    // save unlocked object header into the displaced header location on the stack
    movptr(Address(disp_hdr, 0), hdr);
    // test if object header is still the same (i.e. unlocked), and if so, store the
    // displaced header address in the object header - if it is not the same, get the
    // object header instead
    MacroAssembler::lock(); // must be immediately before cmpxchg!
    cmpxchgptr(disp_hdr, Address(obj, hdr_offset));
    // if the object header was the same, we're done
    jcc(Assembler::equal, done);
    // if the object header was not the same, it is now in the hdr register
    // => test if it is a stack pointer into the same stack (recursive locking), i.e.:
    //
    // 1) (hdr & aligned_mask) == 0
    // 2) rsp <= hdr
    // 3) hdr <= rsp + page_size
    //
    // these 3 tests can be done by evaluating the following expression:
    //
    // (hdr - rsp) & (aligned_mask - page_size)
    //
    // assuming both the stack pointer and page_size have their least
    // significant 2 bits cleared and page_size is a power of 2
    subptr(hdr, rsp);
    andptr(hdr, aligned_mask - (int)os::vm_page_size());
    // for recursive locking, the result is zero => save it in the displaced header
    // location (null in the displaced hdr location indicates recursive locking)
    movptr(Address(disp_hdr, 0), hdr);
    // otherwise we don't care about the result and handle locking via runtime call
    jcc(Assembler::notZero, slow_case);
    // done
    bind(done);
    inc_held_monitor_count();
  }

  return null_check_offset;
}

void C1_MacroAssembler::unlock_object(Register hdr, Register obj, Register disp_hdr, Label& slow_case) {
  const int aligned_mask = BytesPerWord -1;
  const int hdr_offset = oopDesc::mark_offset_in_bytes();
  assert(disp_hdr == rax, "disp_hdr must be rax, for the cmpxchg instruction");
  assert(hdr != obj && hdr != disp_hdr && obj != disp_hdr, "registers must be different");
  Label done;

  if (LockingMode != LM_LIGHTWEIGHT) {
    // load displaced header
    movptr(hdr, Address(disp_hdr, 0));
    // if the loaded hdr is null we had recursive locking
    testptr(hdr, hdr);
    // if we had recursive locking, we are done
    jcc(Assembler::zero, done);
  }

  // load object
  movptr(obj, Address(disp_hdr, BasicObjectLock::obj_offset()));
  verify_oop(obj);

  if (LockingMode == LM_LIGHTWEIGHT) {
    lightweight_unlock(obj, disp_hdr, hdr, slow_case);
  } else if (LockingMode == LM_LEGACY) {
    // test if object header is pointing to the displaced header, and if so, restore
    // the displaced header in the object - if the object header is not pointing to
    // the displaced header, get the object header instead
    MacroAssembler::lock(); // must be immediately before cmpxchg!
    cmpxchgptr(hdr, Address(obj, hdr_offset));
    // if the object header was not pointing to the displaced header,
    // we do unlocking via runtime call
    jcc(Assembler::notEqual, slow_case);
    // done
    bind(done);
    dec_held_monitor_count();
  }
}


// Defines obj, preserves var_size_in_bytes
void C1_MacroAssembler::try_allocate(Register obj, Register var_size_in_bytes, int con_size_in_bytes, Register t1, Register t2, Label& slow_case) {
  if (UseTLAB) {
    tlab_allocate(obj, var_size_in_bytes, con_size_in_bytes, t1, t2, slow_case);
  } else {
    jmp(slow_case);
  }
}


void C1_MacroAssembler::initialize_header(Register obj, Register klass, Register len, Register t1, Register t2) {
  assert_different_registers(obj, klass, len, t1, t2);
  if (UseCompactObjectHeaders) {
    movptr(t1, Address(klass, Klass::prototype_header_offset()));
    movptr(Address(obj, oopDesc::mark_offset_in_bytes()), t1);
  } else if (UseCompressedClassPointers) { // Take care not to kill klass
    movptr(Address(obj, oopDesc::mark_offset_in_bytes()), checked_cast<int32_t>(markWord::prototype().value()));
    movptr(t1, klass);
    encode_klass_not_null(t1, rscratch1);
    movl(Address(obj, oopDesc::klass_offset_in_bytes()), t1);
  } else {
    movptr(Address(obj, oopDesc::mark_offset_in_bytes()), checked_cast<int32_t>(markWord::prototype().value()));
    movptr(Address(obj, oopDesc::klass_offset_in_bytes()), klass);
  }

  if (len->is_valid()) {
    movl(Address(obj, arrayOopDesc::length_offset_in_bytes()), len);
    int base_offset = arrayOopDesc::length_offset_in_bytes() + BytesPerInt;
    if (!is_aligned(base_offset, BytesPerWord)) {
      assert(is_aligned(base_offset, BytesPerInt), "must be 4-byte aligned");
      // Clear gap/first 4 bytes following the length field.
      xorl(t1, t1);
      movl(Address(obj, base_offset), t1);
    }
  } else if (UseCompressedClassPointers && !UseCompactObjectHeaders) {
    xorptr(t1, t1);
    store_klass_gap(obj, t1);
  }
}


// preserves obj, destroys len_in_bytes
void C1_MacroAssembler::initialize_body(Register obj, Register len_in_bytes, int hdr_size_in_bytes, Register t1) {
  assert(hdr_size_in_bytes >= 0, "header size must be positive or 0");
  Label done;

  // len_in_bytes is positive and ptr sized
  subptr(len_in_bytes, hdr_size_in_bytes);
  zero_memory(obj, len_in_bytes, hdr_size_in_bytes, t1);
  bind(done);
}


void C1_MacroAssembler::allocate_object(Register obj, Register t1, Register t2, int header_size, int object_size, Register klass, Label& slow_case) {
  assert(obj == rax, "obj must be in rax, for cmpxchg");
  assert_different_registers(obj, t1, t2); // XXX really?
  assert(header_size >= 0 && object_size >= header_size, "illegal sizes");

  try_allocate(obj, noreg, object_size * BytesPerWord, t1, t2, slow_case);

  initialize_object(obj, klass, noreg, object_size * HeapWordSize, t1, t2, UseTLAB);
}

void C1_MacroAssembler::initialize_object(Register obj, Register klass, Register var_size_in_bytes, int con_size_in_bytes, Register t1, Register t2, bool is_tlab_allocated) {
  assert((con_size_in_bytes & MinObjAlignmentInBytesMask) == 0,
         "con_size_in_bytes is not multiple of alignment");
  const int hdr_size_in_bytes = instanceOopDesc::header_size() * HeapWordSize;
  if (UseCompactObjectHeaders) {
    assert(hdr_size_in_bytes == 8, "check object headers size");
  }
  initialize_header(obj, klass, noreg, t1, t2);

  if (!(UseTLAB && ZeroTLAB && is_tlab_allocated)) {
    // clear rest of allocated space
    const Register t1_zero = t1;
    const Register index = t2;
    const int threshold = 6 * BytesPerWord;   // approximate break even point for code size (see comments below)
    if (var_size_in_bytes != noreg) {
      mov(index, var_size_in_bytes);
      initialize_body(obj, index, hdr_size_in_bytes, t1_zero);
    } else if (con_size_in_bytes <= threshold) {
      // use explicit null stores
      // code size = 2 + 3*n bytes (n = number of fields to clear)
      xorptr(t1_zero, t1_zero); // use t1_zero reg to clear memory (shorter code)
      for (int i = hdr_size_in_bytes; i < con_size_in_bytes; i += BytesPerWord)
        movptr(Address(obj, i), t1_zero);
    } else if (con_size_in_bytes > hdr_size_in_bytes) {
      // use loop to null out the fields
      // code size = 16 bytes for even n (n = number of fields to clear)
      // initialize last object field first if odd number of fields
      xorptr(t1_zero, t1_zero); // use t1_zero reg to clear memory (shorter code)
      movptr(index, (con_size_in_bytes - hdr_size_in_bytes) >> 3);
      // initialize last object field if constant size is odd
      if (((con_size_in_bytes - hdr_size_in_bytes) & 4) != 0)
        movptr(Address(obj, con_size_in_bytes - (1*BytesPerWord)), t1_zero);
      // initialize remaining object fields: rdx is a multiple of 2
      { Label loop;
        bind(loop);
        movptr(Address(obj, index, Address::times_8, hdr_size_in_bytes - (1*BytesPerWord)),
               t1_zero);
        decrement(index);
        jcc(Assembler::notZero, loop);
      }
    }
  }

  if (CURRENT_ENV->dtrace_alloc_probes()) {
    assert(obj == rax, "must be");
    call(RuntimeAddress(Runtime1::entry_for(C1StubId::dtrace_object_alloc_id)));
  }

  verify_oop(obj);
}

void C1_MacroAssembler::allocate_array(Register obj, Register len, Register t1, Register t2, int base_offset_in_bytes, Address::ScaleFactor f, Register klass, Label& slow_case, bool zero_array) {
  assert(obj == rax, "obj must be in rax, for cmpxchg");
  assert_different_registers(obj, len, t1, t2, klass);

  // determine alignment mask
  assert(!(BytesPerWord & 1), "must be a multiple of 2 for masking code to work");

  // check for negative or excessive length
  cmpptr(len, checked_cast<int32_t>(max_array_allocation_length));
  jcc(Assembler::above, slow_case);

  const Register arr_size = t2; // okay to be the same
  // align object end
  movptr(arr_size, base_offset_in_bytes + MinObjAlignmentInBytesMask);
  lea(arr_size, Address(arr_size, len, f));
  andptr(arr_size, ~MinObjAlignmentInBytesMask);

  try_allocate(obj, arr_size, 0, t1, t2, slow_case);

  initialize_header(obj, klass, len, t1, t2);

  // clear rest of allocated space
  if (zero_array) {
    const Register len_zero = len;
    // Align-up to word boundary, because we clear the 4 bytes potentially
    // following the length field in initialize_header().
    int base_offset = align_up(base_offset_in_bytes, BytesPerWord);
    initialize_body(obj, arr_size, base_offset, len_zero);
  }

  if (CURRENT_ENV->dtrace_alloc_probes()) {
    assert(obj == rax, "must be");
    call(RuntimeAddress(Runtime1::entry_for(C1StubId::dtrace_object_alloc_id)));
  }

  verify_oop(obj);
}

void C1_MacroAssembler::build_frame(int frame_size_in_bytes, int bang_size_in_bytes) {
  assert(bang_size_in_bytes >= frame_size_in_bytes, "stack bang size incorrect");
  // Make sure there is enough stack space for this method's activation.
  // Note that we do this before doing an enter(). This matches the
  // ordering of C2's stack overflow check / rsp decrement and allows
  // the SharedRuntime stack overflow handling to be consistent
  // between the two compilers.
  generate_stack_overflow_check(bang_size_in_bytes);

  push(rbp);
  if (PreserveFramePointer) {
    mov(rbp, rsp);
  }
  decrement(rsp, frame_size_in_bytes); // does not emit code for frame_size == 0

  BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
  // C1 code is not hot enough to micro optimize the nmethod entry barrier with an out-of-line stub
  bs->nmethod_entry_barrier(this, nullptr /* slow_path */, nullptr /* continuation */);
}


void C1_MacroAssembler::remove_frame(int frame_size_in_bytes) {
  increment(rsp, frame_size_in_bytes);  // Does not emit code for frame_size == 0
  pop(rbp);
}


void C1_MacroAssembler::verified_entry(bool breakAtEntry) {
  if (breakAtEntry) {
    // Verified Entry first instruction should be 5 bytes long for correct
    // patching by patch_verified_entry().
    //
    // Breakpoint has one byte first instruction.
    // Also first instruction will be one byte "push(rbp)" if stack banging
    // code is not generated (see build_frame() above).
    // For all these cases generate long instruction first.
    fat_nop();
  }
  if (breakAtEntry) int3();
  // build frame
}

void C1_MacroAssembler::load_parameter(int offset_in_words, Register reg) {
  // rbp, + 0: link
  //     + 1: return address
  //     + 2: argument with offset 0
  //     + 3: argument with offset 1
  //     + 4: ...

  movptr(reg, Address(rbp, (offset_in_words + 2) * BytesPerWord));
}

#ifndef PRODUCT

void C1_MacroAssembler::verify_stack_oop(int stack_offset) {
  if (!VerifyOops) return;
  verify_oop_addr(Address(rsp, stack_offset));
}

void C1_MacroAssembler::verify_not_null_oop(Register r) {
  if (!VerifyOops) return;
  Label not_null;
  testptr(r, r);
  jcc(Assembler::notZero, not_null);
  stop("non-null oop required");
  bind(not_null);
  verify_oop(r);
}

void C1_MacroAssembler::invalidate_registers(bool inv_rax, bool inv_rbx, bool inv_rcx, bool inv_rdx, bool inv_rsi, bool inv_rdi) {
#ifdef ASSERT
  if (inv_rax) movptr(rax, 0xDEAD);
  if (inv_rbx) movptr(rbx, 0xDEAD);
  if (inv_rcx) movptr(rcx, 0xDEAD);
  if (inv_rdx) movptr(rdx, 0xDEAD);
  if (inv_rsi) movptr(rsi, 0xDEAD);
  if (inv_rdi) movptr(rdi, 0xDEAD);
#endif
}

#endif // ifndef PRODUCT