Merge clang's isRepeatedBytePattern with LLVM's isBytewiseValue

Summary:
his code was in CGDecl.cpp and really belongs in LLVM's isBytewiseValue. Teach isBytewiseValue the tricks clang's isRepeatedBytePattern had, including merging undef properly, and recursing on more types.

clang part of this patch: D51752

Subscribers: dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D51751

llvm-svn: 342709

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;
         }