1 files changed, 33 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index d760101281a..0d327795acf 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -255,6 +255,39 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
         Worklist.AddValue(EE);
         return CastInst::Create(CI->getOpcode(), EE, EI.getType());
       }
+    } else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
+      if (SI->hasOneUse()) {
+        // TODO: For a select on vectors, it might be useful to do this if it
+        // has multiple extractelement uses. For vector select, that seems to
+        // fight the vectorizer.
+
+        // If we are extracting an element from a vector select or a select on
+        // vectors, create a select on the scalars extracted from the vector
+        // arguments.
+        Value *TrueVal = SI->getTrueValue();
+        Value *FalseVal = SI->getFalseValue();
+
+        Value *Cond = SI->getCondition();
+        if (Cond->getType()->isVectorTy()) {
+          Cond = Builder.CreateExtractElement(Cond,
+                                              EI.getIndexOperand(),
+                                              Cond->getName() + ".elt");
+        }
+
+        Value *V1Elem
+          = Builder.CreateExtractElement(TrueVal,
+                                         EI.getIndexOperand(),
+                                         TrueVal->getName() + ".elt");
+
+        Value *V2Elem
+          = Builder.CreateExtractElement(FalseVal,
+                                         EI.getIndexOperand(),
+                                         FalseVal->getName() + ".elt");
+        return SelectInst::Create(Cond,
+                                  V1Elem,
+                                  V2Elem,
+                                  SI->getName() + ".elt");
+      }
     }
   }
   return nullptr;