Scalar: Ignore ConstantData in processAssumption
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
diff --git a/llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp b/llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
index 9ecaefe..c1df317 100644
--- a/llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
+++ b/llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
@@ -297,6 +297,11 @@
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.