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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
*
* 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.
*/
#ifndef ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
#define ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
#include "base/arena_containers.h"
#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 {
public:
explicit SsaBuilder(HGraph* graph)
: HGraphVisitor(graph),
current_locals_(nullptr),
loop_headers_(graph->GetArena()->Adapter(kArenaAllocSsaBuilder)),
locals_for_(graph->GetBlocks().size(),
ArenaVector<HInstruction*>(graph->GetArena()->Adapter(kArenaAllocSsaBuilder)),
graph->GetArena()->Adapter(kArenaAllocSsaBuilder)) {
loop_headers_.reserve(kDefaultNumberOfLoops);
}
void BuildSsa();
// Returns locals vector for `block`. If it is a catch block, the vector will be
// prepopulated with catch phis for vregs which are defined in `current_locals_`.
ArenaVector<HInstruction*>* GetLocalsFor(HBasicBlock* block);
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";
private:
void SetLoopPhiInputs();
void FixEnvironmentPhis();
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.
ArenaVector<HInstruction*>* 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.
ArenaVector<HBasicBlock*> loop_headers_;
// HEnvironment for each block.
ArenaVector<ArenaVector<HInstruction*>> locals_for_;
DISALLOW_COPY_AND_ASSIGN(SsaBuilder);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
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