[BasicAA] Treat llvm.assume as not accessing memory in getModRefBehavior(Function)
Reviewers: dberlin, chandlerc, hfinkel, reames, sanjoy
Subscribers: mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D19730
llvm-svn: 268068
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 4c6f001..14d92d6 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -575,6 +575,12 @@
if (F->doesNotAccessMemory())
return FMRB_DoesNotAccessMemory;
+ // While the assume intrinsic is marked as arbitrarily writing so that
+ // proper control dependencies will be maintained, it never aliases any
+ // particular memory location.
+ if (F->getIntrinsicID() == Intrinsic::assume)
+ return FMRB_DoesNotAccessMemory;
+
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
// If the function declares it only reads memory, go with that.