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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 <vector>
#include "arch/instruction_set.h"
#include "base/logging.h"
#include "base/macros.h"
#include "arm/constants_arm.h"
#include "managed_register.h"
#include "memory_region.h"
#include "mips/constants_mips.h"
#include "offsets.h"
#include "x86/constants_x86.h"
#include "x86_64/constants_x86_64.h"
#include "dwarf/debug_frame_opcode_writer.h"
namespace art {
class Assembler;
class AssemblerBuffer;
class AssemblerFixup;
namespace arm {
class ArmAssembler;
class Arm32Assembler;
class Thumb2Assembler;
namespace arm64 {
class Arm64Assembler;
namespace mips {
class MipsAssembler;
namespace mips64 {
class Mips64Assembler;
namespace x86 {
class X86Assembler;
namespace x86_64 {
class X86_64Assembler;
class ExternalLabel {
ExternalLabel(const char* name_in, uintptr_t address_in)
: name_(name_in), address_(address_in) {
DCHECK(name_in != nullptr);
const char* name() const { return name_; }
uintptr_t address() const {
return address_;
const char* name_;
const uintptr_t address_;
class Label {
Label() : position_(0) {}
~Label() {
// Assert if label is being destroyed with unresolved branches pending.
// Returns the position for bound and linked labels. Cannot be used
// for unused labels.
int Position() const {
return IsBound() ? -position_ - sizeof(void*) : position_ - sizeof(void*);
int LinkPosition() const {
return position_ - sizeof(void*);
bool IsBound() const { return position_ < 0; }
bool IsUnused() const { return position_ == 0; }
bool IsLinked() const { return position_ > 0; }
int position_;
void Reinitialize() {
position_ = 0;
void BindTo(int position) {
position_ = -position - sizeof(void*);
void LinkTo(int position) {
position_ = position + sizeof(void*);
friend class arm::ArmAssembler;
friend class arm::Arm32Assembler;
friend class arm::Thumb2Assembler;
friend class arm64::Arm64Assembler;
friend class mips::MipsAssembler;
friend class mips64::Mips64Assembler;
friend class x86::X86Assembler;
friend class x86_64::X86_64Assembler;
// Assembler fixups are positions in generated code that require processing
// after the code has been copied to executable memory. This includes building
// relocation information.
class AssemblerFixup {
virtual void Process(const MemoryRegion& region, int position) = 0;
virtual ~AssemblerFixup() {}
AssemblerFixup* previous_;
int position_;
AssemblerFixup* previous() const { return previous_; }
void set_previous(AssemblerFixup* previous_in) { previous_ = previous_in; }
int position() const { return position_; }
void set_position(int position_in) { position_ = position_in; }
friend class AssemblerBuffer;
// Parent of all queued slow paths, emitted during finalization
class SlowPath {
SlowPath() : next_(nullptr) {}
virtual ~SlowPath() {}
Label* Continuation() { return &continuation_; }
Label* Entry() { return &entry_; }
// Generate code for slow path
virtual void Emit(Assembler *sp_asm) = 0;
// Entry branched to by fast path
Label entry_;
// Optional continuation that is branched to at the end of the slow path
Label continuation_;
// Next in linked list of slow paths
SlowPath *next_;
friend class AssemblerBuffer;
class AssemblerBuffer {
// Basic support for emitting, loading, and storing.
template<typename T> void Emit(T value) {
*reinterpret_cast<T*>(cursor_) = value;
cursor_ += sizeof(T);
template<typename T> T Load(size_t position) {
CHECK_LE(position, Size() - static_cast<int>(sizeof(T)));
return *reinterpret_cast<T*>(contents_ + position);
template<typename T> void Store(size_t position, T value) {
CHECK_LE(position, Size() - static_cast<int>(sizeof(T)));
*reinterpret_cast<T*>(contents_ + position) = value;
void Move(size_t newposition, size_t oldposition) {
// Move the contents of the buffer from oldposition to
// newposition by nbytes.
size_t nbytes = Size() - oldposition;
memmove(contents_ + newposition, contents_ + oldposition, nbytes);
cursor_ += newposition - oldposition;
// Emit a fixup at the current location.
void EmitFixup(AssemblerFixup* fixup) {
fixup_ = fixup;
void EnqueueSlowPath(SlowPath* slowpath) {
if (slow_path_ == nullptr) {
slow_path_ = slowpath;
} else {
SlowPath* cur = slow_path_;
for ( ; cur->next_ != nullptr ; cur = cur->next_) {}
cur->next_ = slowpath;
void EmitSlowPaths(Assembler* sp_asm) {
SlowPath* cur = slow_path_;
SlowPath* next = nullptr;
slow_path_ = nullptr;
for ( ; cur != nullptr ; cur = next) {
next = cur->next_;
delete cur;
// Get the size of the emitted code.
size_t Size() const {
CHECK_GE(cursor_, contents_);
return cursor_ - contents_;
uint8_t* contents() const { return contents_; }
// Copy the assembled instructions into the specified memory block
// and apply all fixups.
void FinalizeInstructions(const MemoryRegion& region);
// To emit an instruction to the assembler buffer, the EnsureCapacity helper
// must be used to guarantee that the underlying data area is big enough to
// hold the emitted instruction. Usage:
// AssemblerBuffer buffer;
// AssemblerBuffer::EnsureCapacity ensured(&buffer);
// ... emit bytes for single instruction ...
#ifndef NDEBUG
class EnsureCapacity {
explicit EnsureCapacity(AssemblerBuffer* buffer) {
if (buffer->cursor() >= buffer->limit()) {
// 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;
~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* buffer_;
int gap_;
int ComputeGap() { return buffer_->Capacity() - buffer_->Size(); }
bool has_ensured_capacity_;
bool HasEnsuredCapacity() const { return has_ensured_capacity_; }
class EnsureCapacity {
explicit EnsureCapacity(AssemblerBuffer* buffer) {
if (buffer->cursor() >= buffer->limit()) buffer->ExtendCapacity();
// When building the C++ tests, assertion code is enabled. To allow
// asserting that the user of the assembler buffer has ensured the
// capacity needed for emitting, we add a dummy method in non-debug mode.
bool HasEnsuredCapacity() const { return true; }
// Returns the position in the instruction stream.
int GetPosition() { return cursor_ - contents_; }
// The limit is set to kMinimumGap bytes before the end of the data area.
// This leaves enough space for the longest possible instruction and allows
// for a single, fast space check per instruction.
static const int kMinimumGap = 32;
uint8_t* contents_;
uint8_t* cursor_;
uint8_t* limit_;
AssemblerFixup* fixup_;
#ifndef NDEBUG
bool fixups_processed_;
// Head of linked list of slow paths
SlowPath* slow_path_;
uint8_t* cursor() const { return cursor_; }
uint8_t* limit() const { return limit_; }
size_t Capacity() const {
CHECK_GE(limit_, contents_);
return (limit_ - contents_) + kMinimumGap;
// Process the fixup chain starting at the given fixup. The offset is
// non-zero for fixups in the body if the preamble is non-empty.
void ProcessFixups(const MemoryRegion& region);
// Compute the limit based on the data area and the capacity. See
// description of kMinimumGap for the reasoning behind the value.
static uint8_t* ComputeLimit(uint8_t* data, size_t capacity) {
return data + capacity - kMinimumGap;
void ExtendCapacity();
friend class AssemblerFixup;
// The purpose of this class is to ensure that we do not have to explicitly
// call the AdvancePC method (which is good for convenience and correctness).
class DebugFrameOpCodeWriterForAssembler FINAL
: public dwarf::DebugFrameOpCodeWriter<> {
// This method is called the by the opcode writers.
virtual void ImplicitlyAdvancePC() FINAL;
explicit DebugFrameOpCodeWriterForAssembler(Assembler* buffer)
: dwarf::DebugFrameOpCodeWriter<>(),
assembler_(buffer) {
Assembler* assembler_;
class Assembler {
static Assembler* Create(InstructionSet instruction_set);
// Emit slow paths queued during assembly
virtual void EmitSlowPaths() { buffer_.EmitSlowPaths(this); }
// Size of generated code
virtual size_t CodeSize() const { return buffer_.Size(); }
// Copy instructions out of assembly buffer into the given region of memory
virtual void FinalizeInstructions(const MemoryRegion& region) {
// TODO: Implement with disassembler.
virtual void Comment(const char* format, ...) { UNUSED(format); }
// Emit code that will create an activation on the stack
virtual void BuildFrame(size_t frame_size, ManagedRegister method_reg,
const std::vector<ManagedRegister>& callee_save_regs,
const ManagedRegisterEntrySpills& entry_spills) = 0;
// Emit code that will remove an activation from the stack
virtual void RemoveFrame(size_t frame_size,
const std::vector<ManagedRegister>& callee_save_regs) = 0;
virtual void IncreaseFrameSize(size_t adjust) = 0;
virtual void DecreaseFrameSize(size_t adjust) = 0;
// Store routines
virtual void Store(FrameOffset offs, ManagedRegister src, size_t size) = 0;
virtual void StoreRef(FrameOffset dest, ManagedRegister src) = 0;
virtual void StoreRawPtr(FrameOffset dest, ManagedRegister src) = 0;
virtual void StoreImmediateToFrame(FrameOffset dest, uint32_t imm,
ManagedRegister scratch) = 0;
virtual void StoreImmediateToThread32(ThreadOffset<4> dest, uint32_t imm,
ManagedRegister scratch);
virtual void StoreImmediateToThread64(ThreadOffset<8> dest, uint32_t imm,
ManagedRegister scratch);
virtual void StoreStackOffsetToThread32(ThreadOffset<4> thr_offs,
FrameOffset fr_offs,
ManagedRegister scratch);
virtual void StoreStackOffsetToThread64(ThreadOffset<8> thr_offs,
FrameOffset fr_offs,
ManagedRegister scratch);
virtual void StoreStackPointerToThread32(ThreadOffset<4> thr_offs);
virtual void StoreStackPointerToThread64(ThreadOffset<8> thr_offs);
virtual void StoreSpanning(FrameOffset dest, ManagedRegister src,
FrameOffset in_off, ManagedRegister scratch) = 0;
// Load routines
virtual void Load(ManagedRegister dest, FrameOffset src, size_t size) = 0;
virtual void LoadFromThread32(ManagedRegister dest, ThreadOffset<4> src, size_t size);
virtual void LoadFromThread64(ManagedRegister dest, ThreadOffset<8> src, size_t size);
virtual void LoadRef(ManagedRegister dest, FrameOffset src) = 0;
virtual void LoadRef(ManagedRegister dest, ManagedRegister base, MemberOffset offs) = 0;
virtual void LoadRawPtr(ManagedRegister dest, ManagedRegister base, Offset offs) = 0;
virtual void LoadRawPtrFromThread32(ManagedRegister dest, ThreadOffset<4> offs);
virtual void LoadRawPtrFromThread64(ManagedRegister dest, ThreadOffset<8> offs);
// Copying routines
virtual void Move(ManagedRegister dest, ManagedRegister src, size_t size) = 0;
virtual void CopyRawPtrFromThread32(FrameOffset fr_offs, ThreadOffset<4> thr_offs,
ManagedRegister scratch);
virtual void CopyRawPtrFromThread64(FrameOffset fr_offs, ThreadOffset<8> thr_offs,
ManagedRegister scratch);
virtual void CopyRawPtrToThread32(ThreadOffset<4> thr_offs, FrameOffset fr_offs,
ManagedRegister scratch);
virtual void CopyRawPtrToThread64(ThreadOffset<8> thr_offs, FrameOffset fr_offs,
ManagedRegister scratch);
virtual void CopyRef(FrameOffset dest, FrameOffset src,
ManagedRegister scratch) = 0;
virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch, size_t size) = 0;
virtual void Copy(FrameOffset dest, ManagedRegister src_base, Offset src_offset,
ManagedRegister scratch, size_t size) = 0;
virtual void Copy(ManagedRegister dest_base, Offset dest_offset, FrameOffset src,
ManagedRegister scratch, size_t size) = 0;
virtual void Copy(FrameOffset dest, FrameOffset src_base, Offset src_offset,
ManagedRegister scratch, size_t size) = 0;
virtual void Copy(ManagedRegister dest, Offset dest_offset,
ManagedRegister src, Offset src_offset,
ManagedRegister scratch, size_t size) = 0;
virtual void Copy(FrameOffset dest, Offset dest_offset, FrameOffset src, Offset src_offset,
ManagedRegister scratch, size_t size) = 0;
virtual void MemoryBarrier(ManagedRegister scratch) = 0;
// Sign extension
virtual void SignExtend(ManagedRegister mreg, size_t size) = 0;
// Zero extension
virtual void ZeroExtend(ManagedRegister mreg, size_t size) = 0;
// Exploit fast access in managed code to Thread::Current()
virtual void GetCurrentThread(ManagedRegister tr) = 0;
virtual void GetCurrentThread(FrameOffset dest_offset,
ManagedRegister scratch) = 0;
// Set up out_reg to hold a Object** into the handle scope, or to be null if the
// value is null and null_allowed. in_reg holds a possibly stale reference
// that can be used to avoid loading the handle scope entry to see if the value is
// null.
virtual void CreateHandleScopeEntry(ManagedRegister out_reg, FrameOffset handlescope_offset,
ManagedRegister in_reg, bool null_allowed) = 0;
// Set up out_off to hold a Object** into the handle scope, or to be null if the
// value is null and null_allowed.
virtual void CreateHandleScopeEntry(FrameOffset out_off, FrameOffset handlescope_offset,
ManagedRegister scratch, bool null_allowed) = 0;
// src holds a handle scope entry (Object**) load this into dst
virtual void LoadReferenceFromHandleScope(ManagedRegister dst,
ManagedRegister src) = 0;
// Heap::VerifyObject on src. In some cases (such as a reference to this) we
// know that src may not be null.
virtual void VerifyObject(ManagedRegister src, bool could_be_null) = 0;
virtual void VerifyObject(FrameOffset src, bool could_be_null) = 0;
// Call to address held at [base+offset]
virtual void Call(ManagedRegister base, Offset offset,
ManagedRegister scratch) = 0;
virtual void Call(FrameOffset base, Offset offset,
ManagedRegister scratch) = 0;
virtual void CallFromThread32(ThreadOffset<4> offset, ManagedRegister scratch);
virtual void CallFromThread64(ThreadOffset<8> offset, ManagedRegister scratch);
// Generate code to check if Thread::Current()->exception_ is non-null
// and branch to a ExceptionSlowPath if it is.
virtual void ExceptionPoll(ManagedRegister scratch, size_t stack_adjust) = 0;
virtual ~Assembler() {}
* @brief Buffer of DWARF's Call Frame Information opcodes.
* @details It is used by debuggers and other tools to unwind the call stack.
DebugFrameOpCodeWriterForAssembler& cfi() { return cfi_; }
Assembler() : buffer_(), cfi_(this) {}
AssemblerBuffer buffer_;
DebugFrameOpCodeWriterForAssembler cfi_;
} // namespace art