[llvm] r346698 - [GC][InstCombine] Fix a potential iteration issue

[Philip Reames via llvm-commits]

Author: reames
Date: Mon Nov 12 12:00:53 2018
New Revision: 346698

URL: http://llvm.org/viewvc/llvm-project?rev=346698&view=rev
Log:
[GC][InstCombine] Fix a potential iteration issue

Noticed via inspection.  Appears to be largely innocious in practice, but slight code change could have resulted in either visit order dependent missed optimizations or infinite loops.  May be a minor compile time problem today.


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=346698&r1=346697&r2=346698&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Mon Nov 12 12:00:53 2018
@@ -3902,8 +3902,11 @@ Instruction *InstCombiner::visitCallInst
         return replaceInstUsesWith(*II, ConstantPointerNull::get(PT));
 
       // isKnownNonNull -> nonnull attribute
-      if (isKnownNonZero(DerivedPtr, DL, 0, &AC, II, &DT))
+      if (!II->hasRetAttr(Attribute::NonNull) &&
+          isKnownNonZero(DerivedPtr, DL, 0, &AC, II, &DT)) {
         II->addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
+        return II;
+      }
     }
 
     // TODO: bitcast(relocate(p)) -> relocate(bitcast(p))