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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.
*/
#include "primitive_type_propagation.h"
#include "nodes.h"
#include "ssa_builder.h"
namespace art {
static Primitive::Type MergeTypes(Primitive::Type existing, Primitive::Type new_type) {
// We trust the verifier has already done the necessary checking.
switch (existing) {
case Primitive::kPrimFloat:
case Primitive::kPrimDouble:
case Primitive::kPrimNot:
return existing;
default:
// Phis are initialized with a void type, so if we are asked
// to merge with a void type, we should use the existing one.
return new_type == Primitive::kPrimVoid
? existing
: HPhi::ToPhiType(new_type);
}
}
// Re-compute and update the type of the instruction. Returns
// whether or not the type was changed.
bool PrimitiveTypePropagation::UpdateType(HPhi* phi) {
DCHECK(phi->IsLive());
Primitive::Type existing = phi->GetType();
Primitive::Type new_type = existing;
for (size_t i = 0, e = phi->InputCount(); i < e; ++i) {
Primitive::Type input_type = phi->InputAt(i)->GetType();
new_type = MergeTypes(new_type, input_type);
}
phi->SetType(new_type);
if (new_type == Primitive::kPrimDouble
|| new_type == Primitive::kPrimFloat
|| new_type == Primitive::kPrimNot) {
// If the phi is of floating point type, we need to update its inputs to that
// type. For inputs that are phis, we need to recompute their types.
for (size_t i = 0, e = phi->InputCount(); i < e; ++i) {
HInstruction* input = phi->InputAt(i);
if (input->GetType() != new_type) {
HInstruction* equivalent = (new_type == Primitive::kPrimNot)
? SsaBuilder::GetReferenceTypeEquivalent(input)
: SsaBuilder::GetFloatOrDoubleEquivalent(phi, input, new_type);
phi->ReplaceInput(equivalent, i);
if (equivalent->IsPhi()) {
equivalent->AsPhi()->SetLive();
AddToWorklist(equivalent->AsPhi());
} else if (equivalent == input) {
// The input has changed its type. It can be an input of other phis,
// so we need to put phi users in the work list.
AddDependentInstructionsToWorklist(equivalent);
}
}
}
}
return existing != new_type;
}
void PrimitiveTypePropagation::Run() {
for (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) {
VisitBasicBlock(it.Current());
}
ProcessWorklist();
}
void PrimitiveTypePropagation::VisitBasicBlock(HBasicBlock* block) {
if (block->IsLoopHeader()) {
for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
HPhi* phi = it.Current()->AsPhi();
if (phi->IsLive()) {
AddToWorklist(phi);
}
}
} else {
for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
// Eagerly compute the type of the phi, for quicker convergence. Note
// that we don't need to add users to the worklist because we are
// doing a reverse post-order visit, therefore either the phi users are
// non-loop phi and will be visited later in the visit, or are loop-phis,
// and they are already in the work list.
HPhi* phi = it.Current()->AsPhi();
if (phi->IsLive()) {
UpdateType(phi);
}
}
}
}
void PrimitiveTypePropagation::ProcessWorklist() {
while (!worklist_.IsEmpty()) {
HPhi* instruction = worklist_.Pop();
if (UpdateType(instruction)) {
AddDependentInstructionsToWorklist(instruction);
}
}
}
void PrimitiveTypePropagation::AddToWorklist(HPhi* instruction) {
DCHECK(instruction->IsLive());
worklist_.Add(instruction);
}
void PrimitiveTypePropagation::AddDependentInstructionsToWorklist(HInstruction* instruction) {
for (HUseIterator<HInstruction*> it(instruction->GetUses()); !it.Done(); it.Advance()) {
HPhi* phi = it.Current()->GetUser()->AsPhi();
if (phi != nullptr && phi->IsLive() && phi->GetType() != instruction->GetType()) {
AddToWorklist(phi);
}
}
}
} // namespace art
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