1 files changed, 7 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 6d73091592e..68abf9719a9 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -348,6 +348,9 @@ static APInt getStoreStride(const SCEVAddRecExpr *StoreEv) {
 /// Note that we don't ever attempt to use memset_pattern8 or 4, because these
 /// just replicate their input array and then pass on to memset_pattern16.
 static Constant *getMemSetPatternValue(Value *V, const DataLayout *DL) {
+  // FIXME: This could check for UndefValue because it can be merged into any
+  // other valid pattern.
+
   // If the value isn't a constant, we can't promote it to being in a constant
   // array.  We could theoretically do a store to an alloca or something, but
   // that doesn't seem worthwhile.
@@ -645,9 +648,13 @@ bool LoopIdiomRecognize::processLoopStores(SmallVectorImpl<StoreInst *> &SL,
 
       if (isConsecutiveAccess(SL[i], SL[k], *DL, *SE, false)) {
         if (For == ForMemset::Yes) {
+          if (isa<UndefValue>(FirstSplatValue))
+            FirstSplatValue = SecondSplatValue;
           if (FirstSplatValue != SecondSplatValue)
             continue;
         } else {
+          if (isa<UndefValue>(FirstPatternValue))
+            FirstPatternValue = SecondPatternValue;
           if (FirstPatternValue != SecondPatternValue)
             continue;
         }