[ValueTracking] Calls to @llvm.assume always return

This change teaches llvm::isGuaranteedToTransferExecutionToSuccessor
that calls to @llvm.assume always terminate.  Most other relevant
intrinsics should be covered by the "CS.onlyReadsMemory() ||
CS.onlyAccessesArgMemory()" bit but we were missing @llvm.assumes
because we state that it clobbers memory.

Added an LICM test case, but this change is not specific to LICM.

llvm-svn: 272703

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 7e09ec74bef..7109ff84b8e 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3478,7 +3478,8 @@ bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
     // but it's consistent with other passes. See http://llvm.org/PR965 .
     // FIXME: This isn't aggressive enough; a call which only writes to a
     // global is guaranteed to return.
-    return CS.onlyReadsMemory() || CS.onlyAccessesArgMemory();
+    return CS.onlyReadsMemory() || CS.onlyAccessesArgMemory() ||
+           match(I, m_Intrinsic<Intrinsic::assume>());
   }
 
   // Other instructions return normally.