macro-assembler-ia32.cc.svn-base

Google浏览器V8内核代码

// Copyright 2006-2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#include "bootstrapper.h"
#include "codegen-inl.h"
#include "debug.h"
#include "runtime.h"
#include "serialize.h"

namespace v8 { namespace internal {

MacroAssembler::MacroAssembler(void* buffer, int size)
    : Assembler(buffer, size),
      unresolved_(0),
      generating_stub_(false),
      allow_stub_calls_(true) {
}


static void RecordWriteHelper(MacroAssembler* masm,
                              Register object,
                              Register addr,
                              Register scratch) {
  Label fast;

  // Compute the page address from the heap object pointer, leave it
  // in 'object'.
  masm->and_(object, ~Page::kPageAlignmentMask);

  // Compute the bit addr in the remembered set, leave it in "addr".
  masm->sub(addr, Operand(object));
  masm->shr(addr, kObjectAlignmentBits);

  // If the bit offset lies beyond the normal remembered set range, it is in
  // the extra remembered set area of a large object.
  masm->cmp(addr, Page::kPageSize / kPointerSize);
  masm->j(less, &fast);

  // Adjust 'addr' to be relative to the start of the extra remembered set
  // and the page address in 'object' to be the address of the extra
  // remembered set.
  masm->sub(Operand(addr), Immediate(Page::kPageSize / kPointerSize));
  // Load the array length into 'scratch' and multiply by four to get the
  // size in bytes of the elements.
  masm->mov(scratch, Operand(object, Page::kObjectStartOffset
                                     + FixedArray::kLengthOffset));
  masm->shl(scratch, kObjectAlignmentBits);
  // Add the page header, array header, and array body size to the page
  // address.
  masm->add(Operand(object), Immediate(Page::kObjectStartOffset
                                       + Array::kHeaderSize));
  masm->add(object, Operand(scratch));


  // NOTE: For now, we use the bit-test-and-set (bts) x86 instruction
  // to limit code size. We should probably evaluate this decision by
  // measuring the performance of an equivalent implementation using
  // "simpler" instructions
  masm->bind(&fast);
  masm->bts(Operand(object, 0), addr);
}


class RecordWriteStub : public CodeStub {
 public:
  RecordWriteStub(Register object, Register addr, Register scratch)
      : object_(object), addr_(addr), scratch_(scratch) { }

  void Generate(MacroAssembler* masm);

 private:
  Register object_;
  Register addr_;
  Register scratch_;

  const char* GetName() { return "RecordWriteStub"; }

#ifdef DEBUG
  void Print() {
    PrintF("RecordWriteStub (object reg %d), (addr reg %d), (scratch reg %d)\n",
           object_.code(), addr_.code(), scratch_.code());
  }
#endif

  // Minor key encoding in 12 bits of three registers (object, address and
  // scratch) OOOOAAAASSSS.
  class ScratchBits: public BitField<uint32_t, 0, 4> {};
  class AddressBits: public BitField<uint32_t, 4, 4> {};
  class ObjectBits: public BitField<uint32_t, 8, 4> {
};

  Major MajorKey() { return RecordWrite; }

  int MinorKey() {
    // Encode the registers.
    return ObjectBits::encode(object_.code()) |
           AddressBits::encode(addr_.code()) |
           ScratchBits::encode(scratch_.code());
  }
};


void RecordWriteStub::Generate(MacroAssembler* masm) {
  RecordWriteHelper(masm, object_, addr_, scratch_);
  masm->ret(0);
}


// Set the remembered set bit for [object+offset].
// object is the object being stored into, value is the object being stored.
// If offset is zero, then the scratch register contains the array index into
// the elements array represented as a Smi.
// All registers are clobbered by the operation.
void MacroAssembler::RecordWrite(Register object, int offset,
                                 Register value, Register scratch) {
  // First, check if a remembered set write is even needed. The tests below
  // catch stores of Smis and stores into young gen (which does not have space
  // for the remembered set bits.
  Label done;

  // This optimization cannot survive serialization and deserialization,
  // so we disable as long as serialization can take place.
  int32_t new_space_start =
      reinterpret_cast<int32_t>(ExternalReference::new_space_start().address());
  if (Serializer::enabled() || new_space_start < 0) {
    // Cannot do smart bit-twiddling. Need to do two consecutive checks.
    // Check for Smi first.
    test(value, Immediate(kSmiTagMask));
    j(zero, &done);
    // Test that the object address is not in the new space.  We cannot
    // set remembered set bits in the new space.
    mov(value, Operand(object));
    and_(value, Heap::NewSpaceMask());
    cmp(Operand(value), Immediate(ExternalReference::new_space_start()));
    j(equal, &done);
  } else {
    // move the value SmiTag into the sign bit
    shl(value, 31);
    // combine the object with value SmiTag
    or_(value, Operand(object));
    // remove the uninteresing bits inside the page
    and_(value, Heap::NewSpaceMask() | (1 << 31));
    // xor has two effects:
    // - if the value was a smi, then the result will be negative
    // - if the object is pointing into new space area the page bits will
    //   all be zero
    xor_(value, new_space_start | (1 << 31));
    // Check for both conditions in one branch
    j(less_equal, &done);
  }

  if ((offset > 0) && (offset < Page::kMaxHeapObjectSize)) {
    // Compute the bit offset in the remembered set, leave it in 'value'.
    mov(value, Operand(object));
    and_(value, Page::kPageAlignmentMask);
    add(Operand(value), Immediate(offset));
    shr(value, kObjectAlignmentBits);

    // Compute the page address from the heap object pointer, leave it in
    // 'object'.
    and_(object, ~Page::kPageAlignmentMask);

    // NOTE: For now, we use the bit-test-and-set (bts) x86 instruction
    // to limit code size. We should probably evaluate this decision by
    // measuring the performance of an equivalent implementation using
    // "simpler" instructions
    bts(Operand(object, 0), value);
  } else {
    Register dst = scratch;
    if (offset != 0) {
      lea(dst, Operand(object, offset));
    } else {
      // array access: calculate the destination address in the same manner as
      // KeyedStoreIC::GenerateGeneric
      lea(dst,
          Operand(object, dst, times_2, Array::kHeaderSize - kHeapObjectTag));
    }
    // If we are already generating a shared stub, not inlining the
    // record write code isn't going to save us any memory.
    if (generating_stub()) {
      RecordWriteHelper(this, object, dst, value);
    } else {
      RecordWriteStub stub(object, dst, value);
      CallStub(&stub);
    }
  }

  bind(&done);
}


void MacroAssembler::SaveRegistersToMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of registers to memory location.
  for (int i = 0; i < kNumJSCallerSaved; i++) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      Register reg = { r };
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      mov(Operand::StaticVariable(reg_addr), reg);
    }
  }
}


void MacroAssembler::RestoreRegistersFromMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of memory location to registers.
  for (int i = kNumJSCallerSaved; --i >= 0;) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      Register reg = { r };
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      mov(reg, Operand::StaticVariable(reg_addr));
    }
  }
}


void MacroAssembler::PushRegistersFromMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Push the content of the memory location to the stack.
  for (int i = 0; i < kNumJSCallerSaved; i++) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      push(Operand::StaticVariable(reg_addr));
    }
  }
}


void MacroAssembler::PopRegistersToMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Pop the content from the stack to the memory location.
  for (int i = kNumJSCallerSaved; --i >= 0;) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      pop(Operand::StaticVariable(reg_addr));
    }
  }
}


void MacroAssembler::CopyRegistersFromStackToMemory(Register base,
                                                    Register scratch,
                                                    RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of the stack to the memory location and adjust base.
  for (int i = kNumJSCallerSaved; --i >= 0;) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      mov(scratch, Operand(base, 0));
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      mov(Operand::StaticVariable(reg_addr), scratch);
      lea(base, Operand(base, kPointerSize));
    }
  }
}


void MacroAssembler::Set(Register dst, const Immediate& x) {
  if (x.is_zero()) {
    xor_(dst, Operand(dst));  // shorter than mov
  } else {
    mov(Operand(dst), x);
  }
}


void MacroAssembler::Set(const Operand& dst, const Immediate& x) {
  mov(dst, x);
}


void MacroAssembler::FCmp() {