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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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "base/logging.h"
#include "base/mutex.h"
#include "dex_file-inl.h"
#include "dex_instruction-inl.h"
#include "driver/compiler_driver.h"
#include "driver/dex_compilation_unit.h"
#include "mirror/art_field-inl.h"
#include "mirror/art_method-inl.h"
#include "mirror/class-inl.h"
#include "mirror/dex_cache.h"
namespace art {
namespace optimizer {
// Controls quickening activation.
const bool kEnableQuickening = true;
// Control check-cast elision.
const bool kEnableCheckCastEllision = true;
class DexCompiler {
public:
DexCompiler(art::CompilerDriver& compiler,
const DexCompilationUnit& unit,
DexToDexCompilationLevel dex_to_dex_compilation_level)
: driver_(compiler),
unit_(unit),
dex_to_dex_compilation_level_(dex_to_dex_compilation_level) {}
~DexCompiler() {}
void Compile();
private:
const DexFile& GetDexFile() const {
return *unit_.GetDexFile();
}
// TODO: since the whole compilation pipeline uses a "const DexFile", we need
// to "unconst" here. The DEX-to-DEX compiler should work on a non-const DexFile.
DexFile& GetModifiableDexFile() {
return *const_cast<DexFile*>(unit_.GetDexFile());
}
bool PerformOptimizations() const {
return dex_to_dex_compilation_level_ >= kOptimize;
}
// Compiles a RETURN-VOID into a RETURN-VOID-BARRIER within a constructor where
// a barrier is required.
void CompileReturnVoid(Instruction* inst, uint32_t dex_pc);
// Compiles a CHECK-CAST into 2 NOP instructions if it is known to be safe. In
// this case, returns the second NOP instruction pointer. Otherwise, returns
// the given "inst".
Instruction* CompileCheckCast(Instruction* inst, uint32_t dex_pc);
// Compiles a field access into a quick field access.
// The field index is replaced by an offset within an Object where we can read
// from / write to this field. Therefore, this does not involve any resolution
// at runtime.
// Since the field index is encoded with 16 bits, we can replace it only if the
// field offset can be encoded with 16 bits too.
void CompileInstanceFieldAccess(Instruction* inst, uint32_t dex_pc,
Instruction::Code new_opcode, bool is_put);
// Compiles a virtual method invocation into a quick virtual method invocation.
// The method index is replaced by the vtable index where the corresponding
// AbstractMethod can be found. Therefore, this does not involve any resolution
// at runtime.
// Since the method index is encoded with 16 bits, we can replace it only if the
// vtable index can be encoded with 16 bits too.
void CompileInvokeVirtual(Instruction* inst, uint32_t dex_pc,
Instruction::Code new_opcode, bool is_range);
CompilerDriver& driver_;
const DexCompilationUnit& unit_;
const DexToDexCompilationLevel dex_to_dex_compilation_level_;
DISALLOW_COPY_AND_ASSIGN(DexCompiler);
};
// Ensures write access to a part of DEX file.
//
// If a DEX file is read-only, it modifies its protection (mprotect) so it allows
// write access to the part of DEX file defined by an address and a length.
// In this case, it also takes the DexFile::modification_lock to prevent from
// concurrent protection modification from a parallel DEX-to-DEX compilation on
// the same DEX file.
// When the instance is destroyed, it recovers original protection and releases
// the lock.
// TODO: as this scoped class is similar to a MutexLock we should use annotalysis
// to capture the locking behavior.
class ScopedDexWriteAccess {
public:
ScopedDexWriteAccess(DexFile& dex_file, Instruction* inst,
size_t length)
: dex_file_(dex_file),
address_(reinterpret_cast<uint8_t*>(inst)),
length_(length),
is_read_only_(dex_file_.IsReadOnly()) {
if (is_read_only_) {
// We need to enable DEX write access. To avoid concurrent DEX write access
// modification, we take the DexFile::modification_lock before.
dex_file_.GetModificationLock().ExclusiveLock(Thread::Current());
bool success = dex_file_.EnableWrite(address_, length_);
DCHECK(success) << "Failed to enable DEX write access";
}
}
~ScopedDexWriteAccess() {
DCHECK_EQ(is_read_only_, dex_file_.IsReadOnly());
if (is_read_only_) {
bool success = dex_file_.DisableWrite(address_, length_);
DCHECK(success) << "Failed to disable DEX write access";
// Now we recovered original read-only protection, we can release the
// DexFile::modification_lock.
dex_file_.GetModificationLock().ExclusiveUnlock(Thread::Current());
}
}
private:
DexFile& dex_file_;
// TODO: make address_ const.
uint8_t* address_;
const size_t length_;
const bool is_read_only_;
DISALLOW_COPY_AND_ASSIGN(ScopedDexWriteAccess);
};
void DexCompiler::Compile() {
DCHECK_GE(dex_to_dex_compilation_level_, kRequired);
const DexFile::CodeItem* code_item = unit_.GetCodeItem();
const uint16_t* insns = code_item->insns_;
const uint32_t insns_size = code_item->insns_size_in_code_units_;
Instruction* inst = const_cast<Instruction*>(Instruction::At(insns));
for (uint32_t dex_pc = 0; dex_pc < insns_size;
inst = const_cast<Instruction*>(inst->Next()), dex_pc = inst->GetDexPc(insns)) {
switch (inst->Opcode()) {
case Instruction::RETURN_VOID:
CompileReturnVoid(inst, dex_pc);
break;
case Instruction::CHECK_CAST:
inst = CompileCheckCast(inst, dex_pc);
break;
case Instruction::IGET:
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_QUICK, false);
break;
case Instruction::IGET_WIDE:
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_WIDE_QUICK, false);
break;
case Instruction::IGET_OBJECT:
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_OBJECT_QUICK, false);
break;
case Instruction::IPUT:
case Instruction::IPUT_BOOLEAN:
case Instruction::IPUT_BYTE:
case Instruction::IPUT_CHAR:
case Instruction::IPUT_SHORT:
// These opcodes have the same implementation in interpreter so group
// them under IPUT_QUICK.
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_QUICK, true);
break;
case Instruction::IPUT_WIDE:
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_WIDE_QUICK, true);
break;
case Instruction::IPUT_OBJECT:
CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_OBJECT_QUICK, true);
break;
case Instruction::INVOKE_VIRTUAL:
CompileInvokeVirtual(inst, dex_pc, Instruction::INVOKE_VIRTUAL_QUICK, false);
break;
case Instruction::INVOKE_VIRTUAL_RANGE:
CompileInvokeVirtual(inst, dex_pc, Instruction::INVOKE_VIRTUAL_RANGE_QUICK, true);
break;
default:
// Nothing to do.
break;
}
}
}
void DexCompiler::CompileReturnVoid(Instruction* inst, uint32_t dex_pc) {
DCHECK(inst->Opcode() == Instruction::RETURN_VOID);
// Are we compiling a non-clinit constructor?
if (!unit_.IsConstructor() || unit_.IsStatic()) {
return;
}
// Do we need a constructor barrier ?
if (!driver_.RequiresConstructorBarrier(Thread::Current(), unit_.GetDexFile(),
unit_.GetClassDefIndex())) {
return;
}
// Replace RETURN_VOID by RETURN_VOID_BARRIER.
VLOG(compiler) << "Replacing " << Instruction::Name(inst->Opcode())
<< " by " << Instruction::Name(Instruction::RETURN_VOID_BARRIER)
<< " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
<< PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
ScopedDexWriteAccess sdwa(GetModifiableDexFile(), inst, 2u);
inst->SetOpcode(Instruction::RETURN_VOID_BARRIER);
}
Instruction* DexCompiler::CompileCheckCast(Instruction* inst, uint32_t dex_pc) {
if (!kEnableCheckCastEllision || !PerformOptimizations()) {
return inst;
}
MethodReference referrer(&GetDexFile(), unit_.GetDexMethodIndex());
if (!driver_.IsSafeCast(referrer, dex_pc)) {
return inst;
}
// Ok, this is a safe cast. Since the "check-cast" instruction size is 2 code
// units and a "nop" instruction size is 1 code unit, we need to replace it by
// 2 consecutive NOP instructions.
// Because the caller loops over instructions by calling Instruction::Next onto
// the current instruction, we need to return the 2nd NOP instruction. Indeed,
// its next instruction is the former check-cast's next instruction.
VLOG(compiler) << "Removing " << Instruction::Name(inst->Opcode())
<< " by replacing it with 2 NOPs at dex pc "
<< StringPrintf("0x%x", dex_pc) << " in method "
<< PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
// We are modifying 4 consecutive bytes.
ScopedDexWriteAccess sdwa(GetModifiableDexFile(), inst, 4u);
inst->SetOpcode(Instruction::NOP);
inst->SetVRegA_10x(0u); // keep compliant with verifier.
// Get to next instruction which is the second half of check-cast and replace
// it by a NOP.
inst = const_cast<Instruction*>(inst->Next());
inst->SetOpcode(Instruction::NOP);
inst->SetVRegA_10x(0u); // keep compliant with verifier.
return inst;
}
void DexCompiler::CompileInstanceFieldAccess(Instruction* inst,
uint32_t dex_pc,
Instruction::Code new_opcode,
bool is_put) {
if (!kEnableQuickening || !PerformOptimizations()) {
return;
}
uint32_t field_idx = inst->VRegC_22c();
int field_offset;
bool is_volatile;
bool fast_path = driver_.ComputeInstanceFieldInfo(field_idx, &unit_, field_offset,
is_volatile, is_put);
if (fast_path && !is_volatile && IsUint(16, field_offset)) {
VLOG(compiler) << "Quickening " << Instruction::Name(inst->Opcode())
<< " to " << Instruction::Name(new_opcode)
<< " by replacing field index " << field_idx
<< " by field offset " << field_offset
<< " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
<< PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
// We are modifying 4 consecutive bytes.
ScopedDexWriteAccess sdwa(GetModifiableDexFile(), inst, 4u);
inst->SetOpcode(new_opcode);
// Replace field index by field offset.
inst->SetVRegC_22c(static_cast<uint16_t>(field_offset));
}
}
void DexCompiler::CompileInvokeVirtual(Instruction* inst,
uint32_t dex_pc,
Instruction::Code new_opcode,
bool is_range) {
if (!kEnableQuickening || !PerformOptimizations()) {
return;
}
uint32_t method_idx = is_range ? inst->VRegB_3rc() : inst->VRegB_35c();
MethodReference target_method(&GetDexFile(), method_idx);
InvokeType invoke_type = kVirtual;
InvokeType original_invoke_type = invoke_type;
int vtable_idx;
uintptr_t direct_code;
uintptr_t direct_method;
bool fast_path = driver_.ComputeInvokeInfo(&unit_, dex_pc, invoke_type,
target_method, vtable_idx,
direct_code, direct_method,
false);
// TODO: support devirtualization.
if (fast_path && original_invoke_type == invoke_type) {
if (vtable_idx >= 0 && IsUint(16, vtable_idx)) {
VLOG(compiler) << "Quickening " << Instruction::Name(inst->Opcode())
<< "(" << PrettyMethod(method_idx, GetDexFile(), true) << ")"
<< " to " << Instruction::Name(new_opcode)
<< " by replacing method index " << method_idx
<< " by vtable index " << vtable_idx
<< " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
<< PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
// We are modifying 4 consecutive bytes.
ScopedDexWriteAccess sdwa(GetModifiableDexFile(), inst, 4u);
inst->SetOpcode(new_opcode);
// Replace method index by vtable index.
if (is_range) {
inst->SetVRegB_3rc(static_cast<uint16_t>(vtable_idx));
} else {
inst->SetVRegB_35c(static_cast<uint16_t>(vtable_idx));
}
}
}
}
} // namespace optimizer
} // namespace art
extern "C" void ArtCompileDEX(art::CompilerDriver& compiler, const art::DexFile::CodeItem* code_item,
uint32_t access_flags, art::InvokeType invoke_type,
uint32_t class_def_idx, uint32_t method_idx, jobject class_loader,
const art::DexFile& dex_file,
art::DexToDexCompilationLevel dex_to_dex_compilation_level) {
if (dex_to_dex_compilation_level != art::kDontDexToDexCompile) {
art::DexCompilationUnit unit(NULL, class_loader, art::Runtime::Current()->GetClassLinker(),
dex_file, code_item, class_def_idx, method_idx, access_flags);
art::optimizer::DexCompiler dex_compiler(compiler, unit, dex_to_dex_compilation_level);
dex_compiler.Compile();
}
}