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Use the new addEscapingValue callback to update GlobalsModRef when GVN adds PHIs of GEPs. For the moment,

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have GlobalsModRef handle this conservatively by simply removing the value from its maps.

llvm-svn: 122787
This commit is contained in:
Owen Anderson 2011-01-03 23:51:43 +00:00
parent 5f20fa7fed
commit ce48a5e838
3 changed files with 31 additions and 2 deletions
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11
lib/Analysis/IPA/GlobalsModRef.cpp
View File

@ -152,6 +152,7 @@ namespace {
virtual void deleteValue(Value *V);
virtual void copyValue(Value *From, Value *To);
virtual void addEscapingUse(Use &U);
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
@ -596,3 +597,13 @@ void GlobalsModRef::deleteValue(Value *V) {
void GlobalsModRef::copyValue(Value *From, Value *To) {
AliasAnalysis::copyValue(From, To);
}
void GlobalsModRef::addEscapingUse(Use &U) {
// For the purposes of this analysis, it is conservatively correct to treat
// a newly escaping value equivalently to a deleted one. We could perhaps
// be more precise by processing the new use and attempting to update our
// saved analysis results to accomodate it.
deleteValue(U);
AliasAnalysis::addEscapingUse(U);
}

1
lib/Analysis/NoAliasAnalysis.cpp
View File

@ -65,6 +65,7 @@ namespace {
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
virtual void addEscapingUse(Use &U) {}
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it

21
lib/Transforms/Scalar/GVN.cpp
View File

@ -1063,6 +1063,15 @@ static Value *ConstructSSAForLoadSet(LoadInst *LI,
if (V->getType()->isPointerTy())
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
AA->copyValue(LI, NewPHIs[i]);
// Now that we've copied information to the new PHIs, scan through
// them again and inform alias analysis that we've added potentially
// escaping uses to any values that are operands to these PHIs.
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) {
PHINode *P = NewPHIs[i];
for (unsigned ii = 0, ee = P->getNumIncomingValues(); ii != ee; ++ii)
AA->addEscapingUse(P->getOperandUse(2*ii));
}
return V;
}
@ -1957,8 +1966,16 @@ bool GVN::performPRE(Function &F) {
insert_table(ValNo, Phi, CurrentBlock);
CurInst->replaceAllUsesWith(Phi);
if (MD && Phi->getType()->isPointerTy())
MD->invalidateCachedPointerInfo(Phi);
if (Phi->getType()->isPointerTy()) {
// Because we have added a PHI-use of the pointer value, it has now
// "escaped" from alias analysis' perspective. We need to inform
// AA of this.
for (unsigned ii = 0, ee = Phi->getNumIncomingValues(); ii != ee; ++ii)
VN.getAliasAnalysis()->addEscapingUse(Phi->getOperandUse(2*ii));
if (MD)
MD->invalidateCachedPointerInfo(Phi);
}
VN.erase(CurInst);
erase_table(ValNo, CurInst, CurrentBlock);