commit b8d8db30ea54a9394e5387410d98fcaae6cd7336
author Philip Reames <listmail@philipreames.com> Mon Nov 12 20:00:53 2018 +0000
committer Philip Reames <listmail@philipreames.com> Mon Nov 12 20:00:53 2018 +0000
tree 3bb260c96e7c83a65f534412d752e1829225c5ae
parent c48712b341f328c6095d50bde1947cc523b04014

[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.

llvm-svn: 346698

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index c1872a1..fae47ec 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3902,8 +3902,11 @@
         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))