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Scalar: Ignore ConstantData in processAssumption

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Assumptions on UndefValue and ConstantPointerNull aren't relevant to
other users.  Ignore them entirely to avoid wasting cycles walking
through their (possibly extremely extensive (cross-module)) use-lists.

It wasn't clear how to add a specific test for this, and it'll be
covered anyway by an eventual patch that asserts when trying to access
the use-list of an instance of ConstantData.

llvm-svn: 282334
This commit is contained in:
Duncan P. N. Exon Smith 2016-09-24 20:00:38 +00:00
parent b479873912
commit 4fd9b7e16f
1 changed files with 5 additions and 0 deletions
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5
llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
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@ -297,6 +297,11 @@ bool AlignmentFromAssumptionsPass::processAssumption(CallInst *ACall) {
if (!extractAlignmentInfo(ACall, AAPtr, AlignSCEV, OffSCEV))
return false;
// Skip ConstantPointerNull and UndefValue. Assumptions on these shouldn't
// affect other users.
if (isa<ConstantData>(AAPtr))
return false;
const SCEV *AASCEV = SE->getSCEV(AAPtr);
// Apply the assumption to all other users of the specified pointer.