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// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "hydrogen-deoptimizing-mark.h"
namespace v8 {
namespace internal {
void HPropagateDeoptimizingMarkPhase::MarkAsDeoptimizing() {
HBasicBlock* block = graph()->entry_block();
ZoneList<HBasicBlock*> stack(graph()->blocks()->length(), zone());
while (block != NULL) {
const ZoneList<HBasicBlock*>* dominated_blocks(block->dominated_blocks());
if (!dominated_blocks->is_empty()) {
if (block->IsDeoptimizing()) {
for (int i = 0; i < dominated_blocks->length(); ++i) {
dominated_blocks->at(i)->MarkAsDeoptimizing();
}
}
for (int i = 1; i < dominated_blocks->length(); ++i) {
stack.Add(dominated_blocks->at(i), zone());
}
block = dominated_blocks->at(0);
} else if (!stack.is_empty()) {
// Pop next block from stack.
block = stack.RemoveLast();
} else {
// All blocks processed.
block = NULL;
}
}
}
void HPropagateDeoptimizingMarkPhase::NullifyUnreachableInstructions() {
if (!FLAG_unreachable_code_elimination) return;
for (int i = 0; i < graph()->blocks()->length(); ++i) {
HBasicBlock* block = graph()->blocks()->at(i);
bool nullify = false;
const ZoneList<HBasicBlock*>* predecessors = block->predecessors();
int predecessors_length = predecessors->length();
bool all_predecessors_deoptimizing = (predecessors_length > 0);
for (int j = 0; j < predecessors_length; ++j) {
if (!predecessors->at(j)->IsDeoptimizing()) {
all_predecessors_deoptimizing = false;
break;
}
}
if (all_predecessors_deoptimizing) nullify = true;
for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
HInstruction* instr = it.Current();
// Leave the basic structure of the graph intact.
if (instr->IsBlockEntry()) continue;
if (instr->IsControlInstruction()) continue;
if (instr->IsSimulate()) continue;
if (instr->IsEnterInlined()) continue;
if (instr->IsLeaveInlined()) continue;
if (nullify) {
HInstruction* last_dummy = NULL;
for (int j = 0; j < instr->OperandCount(); ++j) {
HValue* operand = instr->OperandAt(j);
// Insert an HDummyUse for each operand, unless the operand
// is an HDummyUse itself. If it's even from the same block,
// remember it as a potential replacement for the instruction.
if (operand->IsDummyUse()) {
if (operand->block() == instr->block() &&
last_dummy == NULL) {
last_dummy = HInstruction::cast(operand);
}
continue;
}
if (operand->IsControlInstruction()) {
// Inserting a dummy use for a value that's not defined anywhere
// will fail. Some instructions define fake inputs on such
// values as control flow dependencies.
continue;
}
HDummyUse* dummy = new(graph()->zone()) HDummyUse(operand);
dummy->InsertBefore(instr);
last_dummy = dummy;
}
if (last_dummy == NULL) last_dummy = graph()->GetConstant1();
instr->DeleteAndReplaceWith(last_dummy);
continue;
}
if (instr->IsSoftDeoptimize()) {
ASSERT(block->IsDeoptimizing());
nullify = true;
}
}
}
}
void HPropagateDeoptimizingMarkPhase::Run() {
// Skip this phase if there is nothing to be done anyway.
if (!graph()->has_soft_deoptimize()) return;
MarkAsDeoptimizing();
NullifyUnreachableInstructions();
}
} } // namespace v8::internal
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