Simplify demanded bits of select sources where the condition is a constant vector

llvm-svn: 160835

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index eb9945b6817..bdd97a862b7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -899,5 +899,16 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
     return &SI;
   }
 
+  if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) {
+    unsigned VWidth = VecTy->getNumElements();
+    APInt UndefElts(VWidth, 0);
+    APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
+    if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
+      if (V != &SI)
+        return ReplaceInstUsesWith(SI, V);
+      return &SI;
+    }
+  }
+
   return 0;
 }