Commit 6749dc34 authored by Craig Topper's avatar Craig Topper
Browse files

[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
parent 2f32da3d

llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp

+3 −2
Original line number Diff line number Diff line
@@ -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())));

llvm/test/Transforms/InstCombine/bitcast-vec-canon.ll

+2 −4
Original line number Diff line number Diff line
@@ -40,8 +40,7 @@ define <1 x i64> @d(i64 %y) { 


define x86_mmx @e(<1 x i64> %y) {

; CHECK-LABEL: @e(

; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <1 x i64> %y, i32 0

; CHECK-NEXT:    [[C:%.*]] = bitcast i64 [[TMP1]] to x86_mmx

; CHECK-NEXT:    [[C:%.*]] = bitcast <1 x i64> %y to x86_mmx

; CHECK-NEXT:    ret x86_mmx [[C]]

;

  %c = bitcast <1 x i64> %y to x86_mmx
@@ -50,8 +49,7 @@ define x86_mmx @e(<1 x i64> %y) { 


define <1 x i64> @f(x86_mmx %y) {

; CHECK-LABEL: @f(

; CHECK-NEXT:    [[TMP1:%.*]] = bitcast x86_mmx %y to i64

; CHECK-NEXT:    [[C:%.*]] = insertelement <1 x i64> undef, i64 [[TMP1]], i32 0

; CHECK-NEXT:    [[C:%.*]] = bitcast x86_mmx %y to <1 x i64>

; CHECK-NEXT:    ret <1 x i64> [[C]]

;

  %c = bitcast x86_mmx %y to <1 x i64>