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* Copyright (C) 2014 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 "nodes.h"
#include "optimization.h"
namespace art {
static constexpr int kDefaultNumberOfLoops = 2;
* Transforms a graph into SSA form. The liveness guarantees of
* this transformation are listed below. A DEX register
* being killed means its value at a given position in the code
* will not be available to its environment uses. A merge in the
* following text is materialized as a `HPhi`.
* (a) Dex registers that do not require merging (that is, they do not
* have different values at a join block) are available to all their
* environment uses. Note that it does not imply the instruction will
* have a physical location after register allocation. See the
* SsaLivenessAnalysis phase.
* (b) Dex registers that require merging, and the merging gives
* incompatible types, will be killed for environment uses of that merge.
* (c) When the `debuggable` flag is passed to the compiler, Dex registers
* that require merging and have a proper type after the merge, are
* available to all their environment uses. If the `debuggable` flag
* is not set, values of Dex registers only used by environments
* are killed.
class SsaBuilder : public HGraphVisitor {
explicit SsaBuilder(HGraph* graph)
: HGraphVisitor(graph),
loop_headers_(graph->GetArena(), kDefaultNumberOfLoops),
locals_for_(graph->GetArena(), graph->GetBlocks().Size()) {
void BuildSsa();
HEnvironment* GetLocalsFor(HBasicBlock* block) {
HEnvironment* env = locals_for_.Get(block->GetBlockId());
if (env == nullptr) {
env = new (GetGraph()->GetArena()) HEnvironment(
GetGraph()->GetArena(), GetGraph()->GetNumberOfVRegs());
locals_for_.Put(block->GetBlockId(), env);
return env;
HInstruction* ValueOfLocal(HBasicBlock* block, size_t local);
void VisitBasicBlock(HBasicBlock* block);
void VisitLoadLocal(HLoadLocal* load);
void VisitStoreLocal(HStoreLocal* store);
void VisitInstruction(HInstruction* instruction);
void VisitTemporary(HTemporary* instruction);
static HInstruction* GetFloatOrDoubleEquivalent(HInstruction* user,
HInstruction* instruction,
Primitive::Type type);
static HInstruction* GetReferenceTypeEquivalent(HInstruction* instruction);
static constexpr const char* kSsaBuilderPassName = "ssa_builder";
void FixNullConstantType();
void EquivalentPhisCleanup();
static HFloatConstant* GetFloatEquivalent(HIntConstant* constant);
static HDoubleConstant* GetDoubleEquivalent(HLongConstant* constant);
static HPhi* GetFloatDoubleOrReferenceEquivalentOfPhi(HPhi* phi, Primitive::Type type);
// Locals for the current block being visited.
HEnvironment* current_locals_;
// Keep track of loop headers found. The last phase of the analysis iterates
// over these blocks to set the inputs of their phis.
GrowableArray<HBasicBlock*> loop_headers_;
// HEnvironment for each block.
GrowableArray<HEnvironment*> locals_for_;
} // namespace art