[InstCombine] Don't transform bitcasts between x86_mmx and v1i64 into insertelement/extractelement

x86_mmx is conceptually a vector already. Don't introduce an extra conversion between it and scalar i64.

I'm using VectorType::isValidElementType which checks for floating point, integer, and pointers to hopefully make this more readable than just blacklisting x86_mmx.

Differential Revision: https://reviews.llvm.org/D69964

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 65aaef28d87..0390368c4bb 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2359,7 +2359,8 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
   }
 
   if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
-    if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
+    if (DestVTy->getNumElements() == 1 &&
+        VectorType::isValidElementType(SrcTy)) {
       Value *Elem = Builder.CreateBitCast(Src, DestVTy->getElementType());
       return InsertElementInst::Create(UndefValue::get(DestTy), Elem,
                      Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
@@ -2391,7 +2392,7 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     if (SrcVTy->getNumElements() == 1) {
       // If our destination is not a vector, then make this a straight
       // scalar-scalar cast.
-      if (!DestTy->isVectorTy()) {
+      if (VectorType::isValidElementType(DestTy)) {
         Value *Elem =
           Builder.CreateExtractElement(Src,
                      Constant::getNullValue(Type::getInt32Ty(CI.getContext())));