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Bug 1068960 - IonMonkey: GVN: Re-establish the original dependency after foldsTo is done r=nbp

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This commit is contained in:
Dan Gohman 2014-09-18 08:51:37 -07:00
parent 6ab71bfc99
commit 690cff68f3
1 changed files with 11 additions and 2 deletions
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13
js/src/jit/ValueNumbering.cpp
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@ -700,7 +700,7 @@ ValueNumberer::visitDefinition(MDefinition *def)
{
// If this instruction has a dependency() into an unreachable block, we'll
// need to update AliasAnalysis.
const MDefinition *dep = def->dependency();
MDefinition *dep = def->dependency();
if (dep != nullptr && (dep->isDiscarded() || dep->block()->isDead())) {
JitSpew(JitSpew_GVN, " AliasAnalysis invalidated");
if (updateAliasAnalysis_ && !dependenciesBroken_) {
@ -709,8 +709,11 @@ ValueNumberer::visitDefinition(MDefinition *def)
JitSpew(JitSpew_GVN, " Will recompute!");
dependenciesBroken_ = true;
}
// Clear its dependency for now, to protect foldsTo.
// Temporarily clear its dependency, to protect foldsTo, which may
// wish to use the dependency to do store-to-load forwarding.
def->setDependency(def->toInstruction());
} else {
dep = nullptr;
}
// Look for a simplified form of |def|.
@ -741,6 +744,12 @@ ValueNumberer::visitDefinition(MDefinition *def)
def = sim;
}
// Now that foldsTo is done, re-enable the original dependency. Even though
// it may be pointing into a discarded block, it's still valid for the
// purposes of detecting congruent loads.
if (dep != nullptr)
def->setDependency(dep);
// Look for a dominating def which makes |def| redundant.
MDefinition *rep = leader(def);
if (rep != def) {