119 lines
4.1 KiB
C++
119 lines
4.1 KiB
C++
/*
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* Copyright (C) 2015-2019 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#include "B3EliminateDeadCode.h"
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#if ENABLE(B3_JIT)
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#include "B3BasicBlock.h"
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#include "B3PhaseScope.h"
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#include "B3ValueInlines.h"
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#include "B3Variable.h"
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#include "B3VariableValue.h"
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#include <wtf/GraphNodeWorklist.h>
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#include <wtf/IndexSet.h>
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#include <wtf/Vector.h>
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namespace JSC { namespace B3 {
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// FIXME: this pass currently only eliminates values and variables, it does not seem to eliminate dead blocks.
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bool eliminateDeadCodeImpl(Procedure& proc)
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{
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bool changed = false;
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GraphNodeWorklist<Value*, IndexSet<Value*>> worklist;
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Vector<UpsilonValue*, 64> upsilons;
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for (BasicBlock* block : proc) {
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for (Value* value : *block) {
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Effects effects;
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// We don't care about effects of SSA operations, since we model them more
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// accurately than the effects() method does.
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if (value->opcode() != Phi && value->opcode() != Upsilon)
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effects = value->effects();
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if (effects.mustExecute())
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worklist.push(value);
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if (UpsilonValue* upsilon = value->as<UpsilonValue>())
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upsilons.append(upsilon);
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}
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}
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for (;;) {
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while (Value* value = worklist.pop()) {
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for (Value* child : value->children())
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worklist.push(child);
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}
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bool didPush = false;
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for (size_t upsilonIndex = 0; upsilonIndex < upsilons.size(); ++upsilonIndex) {
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UpsilonValue* upsilon = upsilons[upsilonIndex];
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if (worklist.saw(upsilon->phi())) {
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worklist.push(upsilon);
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upsilons[upsilonIndex--] = upsilons.last();
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upsilons.takeLast();
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didPush = true;
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}
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}
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if (!didPush)
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break;
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}
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IndexSet<Variable*> liveVariables;
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for (BasicBlock* block : proc) {
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size_t sourceIndex = 0;
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size_t targetIndex = 0;
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while (sourceIndex < block->size()) {
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Value* value = block->at(sourceIndex++);
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if (worklist.saw(value)) {
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if (VariableValue* variableValue = value->as<VariableValue>())
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liveVariables.add(variableValue->variable());
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block->at(targetIndex++) = value;
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} else {
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proc.deleteValue(value);
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changed = true;
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}
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}
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block->values().resize(targetIndex);
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}
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for (Variable* variable : proc.variables()) {
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if (!liveVariables.contains(variable))
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proc.deleteVariable(variable);
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}
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return changed;
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}
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bool eliminateDeadCode(Procedure& proc)
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{
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PhaseScope phaseScope(proc, "eliminateDeadCode");
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return eliminateDeadCodeImpl(proc);
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}
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} } // namespace JSC::B3
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#endif // ENABLE(B3_JIT)
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