105 lines
3.6 KiB
C++
105 lines
3.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: set ts=8 sts=4 et sw=4 tw=99:
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "jit/FoldLinearArithConstants.h"
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#include "jit/IonAnalysis.h"
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#include "jit/MIR.h"
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#include "jit/MIRGenerator.h"
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#include "jit/MIRGraph.h"
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using namespace js;
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using namespace jit;
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namespace js {
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namespace jit {
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// Mark this node and its children as RecoveredOnBailout when they are not used.
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// The marked nodes will be removed during DCE. Marking as RecoveredOnBailout is
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// necessary because the Sink pass is ran before this pass.
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static void
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markNodesAsRecoveredOnBailout(MDefinition* def)
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{
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if (def->hasLiveDefUses() || !DeadIfUnused(def) || !def->canRecoverOnBailout())
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return;
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JitSpew(JitSpew_FLAC, "mark as recovered on bailout: %s%u", def->opName(), def->id());
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def->setRecoveredOnBailoutUnchecked();
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// Recursively mark nodes that do not have multiple uses. This loop is
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// necessary because a node could be an unused right shift zero or an
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// unused add, and both need to be marked as RecoveredOnBailout.
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for (size_t i = 0; i < def->numOperands(); i++)
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markNodesAsRecoveredOnBailout(def->getOperand(i));
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}
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// Fold AddIs with one variable and two or more constants into one AddI.
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static void
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AnalyzeAdd(TempAllocator& alloc, MAdd* add)
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{
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if (add->specialization() != MIRType::Int32 || add->isRecoveredOnBailout())
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return;
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if (!add->hasUses())
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return;
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JitSpew(JitSpew_FLAC, "analyze add: %s%u", add->opName(), add->id());
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SimpleLinearSum sum = ExtractLinearSum(add);
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if (sum.constant == 0 || !sum.term)
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return;
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// Determine which operand is the constant.
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int idx = add->getOperand(0)->isConstant() ? 0 : 1 ;
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if (add->getOperand(idx)->isConstant()) {
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// Do not replace an add where the outcome is the same add instruction.
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MOZ_ASSERT(add->getOperand(idx)->toConstant()->type() == MIRType::Int32);
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if (sum.term == add->getOperand(1 - idx) ||
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sum.constant == add->getOperand(idx)->toConstant()->toInt32())
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{
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return;
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}
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}
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MInstruction* rhs = MConstant::New(alloc, Int32Value(sum.constant));
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add->block()->insertBefore(add, rhs);
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MAdd* addNew = MAdd::New(alloc, sum.term, rhs, MIRType::Int32);
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add->replaceAllLiveUsesWith(addNew);
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add->block()->insertBefore(add, addNew);
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JitSpew(JitSpew_FLAC, "replaced with: %s%u", addNew->opName(), addNew->id());
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JitSpew(JitSpew_FLAC, "and constant: %s%u (%d)", rhs->opName(), rhs->id(), sum.constant);
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// Mark the stale nodes as RecoveredOnBailout since the Sink pass has
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// been run before this pass. DCE will then remove the unused nodes.
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markNodesAsRecoveredOnBailout(add);
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}
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bool
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FoldLinearArithConstants(MIRGenerator* mir, MIRGraph& graph)
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{
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for (PostorderIterator block(graph.poBegin()); block != graph.poEnd(); block++) {
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if (mir->shouldCancel("Fold Linear Arithmetic Constants (main loop)"))
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return false;
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for (MInstructionIterator i = block->begin(); i != block->end(); i++) {
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if (!graph.alloc().ensureBallast())
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return false;
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if (mir->shouldCancel("Fold Linear Arithmetic Constants (inner loop)"))
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return false;
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if (i->isAdd())
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AnalyzeAdd(graph.alloc(), i->toAdd());
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}
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}
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return true;
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}
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} /* namespace jit */
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} /* namespace js */
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