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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "jit/FoldLinearArithConstants.h"
#include "jit/IonAnalysis.h"
#include "jit/MIR.h"
#include "jit/MIRGenerator.h"
#include "jit/MIRGraph.h"
using namespace js;
using namespace jit;
namespace js {
namespace jit {
// Mark this node and its children as RecoveredOnBailout when they are not used.
// The marked nodes will be removed during DCE. Marking as RecoveredOnBailout is
// necessary because the Sink pass is ran before this pass.
static void markNodesAsRecoveredOnBailout(MDefinition* def) {
if (def->hasLiveDefUses() || !DeadIfUnused(def) ||
!def->canRecoverOnBailout()) {
return;
}
JitSpew(JitSpew_FLAC, "mark as recovered on bailout: %s%u", def->opName(),
def->id());
def->setRecoveredOnBailoutUnchecked();
// Recursively mark nodes that do not have multiple uses. This loop is
// necessary because a node could be an unused right shift zero or an
// unused add, and both need to be marked as RecoveredOnBailout.
for (size_t i = 0; i < def->numOperands(); i++) {
markNodesAsRecoveredOnBailout(def->getOperand(i));
}
}
// Fold AddIs with one variable and two or more constants into one AddI.
static void AnalyzeAdd(TempAllocator& alloc, MAdd* add) {
if (add->type() != MIRType::Int32 || add->isRecoveredOnBailout()) {
return;
}
if (!add->hasUses()) {
return;
}
JitSpew(JitSpew_FLAC, "analyze add: %s%u", add->opName(), add->id());
SimpleLinearSum sum = ExtractLinearSum(add);
if (sum.constant == 0 || !sum.term) {
return;
}
// Determine which operand is the constant.
int idx = add->getOperand(0)->isConstant() ? 0 : 1;
if (add->getOperand(idx)->isConstant()) {
// Do not replace an add where the outcome is the same add instruction.
MOZ_ASSERT(add->getOperand(idx)->toConstant()->type() == MIRType::Int32);
if (sum.term == add->getOperand(1 - idx) ||
sum.constant == add->getOperand(idx)->toConstant()->toInt32()) {
return;
}
}
MInstruction* rhs = MConstant::New(alloc, Int32Value(sum.constant));
add->block()->insertBefore(add, rhs);
MAdd* addNew = MAdd::New(alloc, sum.term, rhs, add->truncateKind());
addNew->setBailoutKind(add->bailoutKind());
add->replaceAllLiveUsesWith(addNew);
add->block()->insertBefore(add, addNew);
JitSpew(JitSpew_FLAC, "replaced with: %s%u", addNew->opName(), addNew->id());
JitSpew(JitSpew_FLAC, "and constant: %s%u (%d)", rhs->opName(), rhs->id(),
sum.constant);
// Mark the stale nodes as RecoveredOnBailout since the Sink pass has
// been run before this pass. DCE will then remove the unused nodes.
markNodesAsRecoveredOnBailout(add);
}
bool FoldLinearArithConstants(MIRGenerator* mir, MIRGraph& graph) {
JitSpew(JitSpew_FLAC, "Begin");
for (PostorderIterator block(graph.poBegin()); block != graph.poEnd();
block++) {
if (mir->shouldCancel("Fold Linear Arithmetic Constants (main loop)")) {
return false;
}
for (MInstructionIterator i = block->begin(); i != block->end(); i++) {
if (!graph.alloc().ensureBallast()) {
return false;
}
if (mir->shouldCancel("Fold Linear Arithmetic Constants (inner loop)")) {
return false;
}
if (i->isAdd()) {
AnalyzeAdd(graph.alloc(), i->toAdd());
}
}
}
return true;
}
} /* namespace jit */
} /* namespace js */