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* Copyright (C) 2011 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "assembler.h"
#include <algorithm>
#include <vector>
#include "assembler_arm.h"
#include "assembler_x86.h"
#include "globals.h"
#include "memory_region.h"
namespace art {
static byte* NewContents(size_t capacity) {
byte* result = new byte[capacity];
#if defined(DEBUG)
// Initialize the buffer with kBreakPointInstruction to force a break
// point if we ever execute an uninitialized part of the code buffer.
Assembler::InitializeMemoryWithBreakpoints(result, capacity);
return result;
#if defined(DEBUG)
AssemblerBuffer::EnsureCapacity::EnsureCapacity(AssemblerBuffer* buffer) {
if (buffer->cursor() >= buffer->limit()) buffer->ExtendCapacity();
// In debug mode, we save the assembler buffer along with the gap
// size before we start emitting to the buffer. This allows us to
// check that any single generated instruction doesn't overflow the
// limit implied by the minimum gap size.
buffer_ = buffer;
gap_ = ComputeGap();
// Make sure that extending the capacity leaves a big enough gap
// for any kind of instruction.
CHECK_GE(gap_, kMinimumGap);
// Mark the buffer as having ensured the capacity.
CHECK(!buffer->HasEnsuredCapacity()); // Cannot nest.
buffer->has_ensured_capacity_ = true;
AssemblerBuffer::EnsureCapacity::~EnsureCapacity() {
// Unmark the buffer, so we cannot emit after this.
buffer_->has_ensured_capacity_ = false;
// Make sure the generated instruction doesn't take up more
// space than the minimum gap.
int delta = gap_ - ComputeGap();
CHECK_LE(delta, kMinimumGap);
AssemblerBuffer::AssemblerBuffer() {
static const size_t kInitialBufferCapacity = 4 * KB;
contents_ = NewContents(kInitialBufferCapacity);
cursor_ = contents_;
limit_ = ComputeLimit(contents_, kInitialBufferCapacity);
fixup_ = NULL;
slow_path_ = NULL;
#if defined(DEBUG)
has_ensured_capacity_ = false;
fixups_processed_ = false;
// Verify internal state.
CHECK_EQ(Capacity(), kInitialBufferCapacity);
CHECK_EQ(Size(), 0U);
AssemblerBuffer::~AssemblerBuffer() {
delete[] contents_;
void AssemblerBuffer::ProcessFixups(const MemoryRegion& region) {
AssemblerFixup* fixup = fixup_;
while (fixup != NULL) {
fixup->Process(region, fixup->position());
fixup = fixup->previous();
void AssemblerBuffer::FinalizeInstructions(const MemoryRegion& instructions) {
// Copy the instructions from the buffer.
MemoryRegion from(reinterpret_cast<void*>(contents()), Size());
instructions.CopyFrom(0, from);
// Process fixups in the instructions.
#if defined(DEBUG)
fixups_processed_ = true;
void AssemblerBuffer::ExtendCapacity() {
size_t old_size = Size();
size_t old_capacity = Capacity();
size_t new_capacity = std::min(old_capacity * 2, old_capacity + 1 * MB);
// Allocate the new data area and copy contents of the old one to it.
byte* new_contents = NewContents(new_capacity);
// Compute the relocation delta and switch to the new contents area.
ptrdiff_t delta = new_contents - contents_;
contents_ = new_contents;
// Update the cursor and recompute the limit.
cursor_ += delta;
limit_ = ComputeLimit(new_contents, new_capacity);
// Verify internal state.
CHECK_EQ(Capacity(), new_capacity);
CHECK_EQ(Size(), old_size);
Assembler* Assembler::Create(InstructionSet instruction_set) {
if (instruction_set == kX86) {
return new x86::X86Assembler();
} else {
CHECK(instruction_set == kArm || instruction_set == kThumb2);
return new arm::ArmAssembler();
} // namespace art