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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();
ArenaVector<HInstruction*>* GetLocalsFor(HBasicBlock* block) {
DCHECK_LT(block->GetBlockId(), locals_for_.size());
ArenaVector<HInstruction*>* locals = &locals_for_[block->GetBlockId()];
if (locals->empty() && GetGraph()->GetNumberOfVRegs() != 0u) {
const size_t vregs = GetGraph()->GetNumberOfVRegs();
locals->resize(vregs, nullptr);
if (block->IsCatchBlock()) {
// We record incoming inputs of catch phis at throwing instructions and
// must therefore eagerly create the phis. Unused phis will be removed
// in the dead phi analysis.
ArenaAllocator* arena = GetGraph()->GetArena();
for (size_t i = 0; i < vregs; ++i) {
HPhi* phi = new (arena) HPhi(arena, i, 0, Primitive::kPrimVoid);
block->AddPhi(phi);
(*locals)[i] = phi;
}
}
}
return locals;
}
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 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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