Add tests, remove comment

Author: ckoparkar

llvm/lib/Transforms/Vectorize/VectorCombine.cpp

@@ -2487,10 +2487,8 @@ bool VectorCombine::foldShuffleOfCastops(Instruction &I) {
   if (!match(&I, m_Shuffle(m_Value(V0), m_Value(V1), m_Mask(OldMask))))
     return false;
 
-  // Check whether this is a unary shuffle.
-  // TODO: check if this can be extended to match undef or unused values,
-  // perhaps using ShuffleVectorInst::isSingleSource.
-  bool IsBinaryShuffle = !isa<PoisonValue>(V1);
+  // Check whether this is a binary shuffle.
+  bool IsBinaryShuffle = !isa<UndefValue>(V1);
 
   auto *C0 = dyn_cast<CastInst>(V0);
   auto *C1 = dyn_cast<CastInst>(V1);
@@ -2501,9 +2499,8 @@ bool VectorCombine::foldShuffleOfCastops(Instruction &I) {
 
   // If this is allowed, foldShuffleOfCastops can get stuck in a loop
   // with foldBitcastOfShuffle. Reject in favor of foldBitcastOfShuffle.
-  if (!IsBinaryShuffle && Opcode == Instruction::BitCast) {
+  if (!IsBinaryShuffle && Opcode == Instruction::BitCast)
     return false;
-  }
 
   if (IsBinaryShuffle) {
     if (C0->getSrcTy() != C1->getSrcTy())

llvm/test/Transforms/VectorCombine/X86/shuffle-of-casts.ll

@@ -342,3 +342,71 @@ define <16 x i32> @concat_sext_zext_v8i16_v16i32(<8 x i16> %a0, <8 x i16> %a1) {
   %r = shufflevector <8 x i32> %x0, <8 x i32> %x1, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
   ret <16 x i32> %r
 }
+
+; Unary shuffles
+
+define <4 x i16> @unary_shuffle_zext_v8i8_v4i16(<8 x i8> %a0) {
+; CHECK-LABEL: define <4 x i16> @unary_shuffle_zext_v8i8_v4i16(
+; CHECK-SAME: <8 x i8> [[A0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[VEC_SHUFFLE:%.*]] = shufflevector <8 x i8> [[A0]], <8 x i8> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT: [[X1:%.*]] = zext <4 x i8> [[VEC_SHUFFLE]] to <4 x i16>
+; CHECK-NEXT: ret <4 x i16> [[X1]]
+;
+  %x1 = zext <8 x i8> %a0 to <8 x i16>
+  %vec.shuffle = shufflevector <8 x i16> %x1, <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  ret <4 x i16> %vec.shuffle
+}
+
+define <4 x i16> @unary_shuffle_sext_v8i8_v4i16(<8 x i8> %a0) {
+; CHECK-LABEL: define <4 x i16> @unary_shuffle_sext_v8i8_v4i16(
+; CHECK-SAME: <8 x i8> [[A0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[VEC_SHUFFLE:%.*]] = shufflevector <8 x i8> [[A0]], <8 x i8> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT: [[X1:%.*]] = sext <4 x i8> [[VEC_SHUFFLE]] to <4 x i16>
+; CHECK-NEXT: ret <4 x i16> [[X1]]
+;
+  %x1 = sext <8 x i8> %a0 to <8 x i16>
+  %vec.shuffle = shufflevector <8 x i16> %x1, <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  ret <4 x i16> %vec.shuffle
+}
+
+define <4 x i16> @unary_shuffle_sext_v8i8_v4i16_undef(<8 x i8> %a0) {
+; CHECK-LABEL: define <4 x i16> @unary_shuffle_sext_v8i8_v4i16_undef(
+; CHECK-SAME: <8 x i8> [[A0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[VEC_SHUFFLE:%.*]] = shufflevector <8 x i8> [[A0]], <8 x i8> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT: [[X1:%.*]] = sext <4 x i8> [[VEC_SHUFFLE]] to <4 x i16>
+; CHECK-NEXT: ret <4 x i16> [[X1]]
+;
+  %x1 = sext <8 x i8> %a0 to <8 x i16>
+  %vec.shuffle = shufflevector <8 x i16> %x1, <8 x i16> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  ret <4 x i16> %vec.shuffle
+}
+
+; negative - avoid loop with foldBitcastOfShuffle
+
+define <2 x i32> @unary_shuffle_bitcast_v8i8_v2i32(<8 x i8> %a0) {
+; CHECK-LABEL: define <2 x i32> @unary_shuffle_bitcast_v8i8_v2i32(
+; CHECK-SAME: <8 x i8> [[A0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[X1:%.*]] = bitcast <8 x i8> [[A0]] to <2 x i32>
+; CHECK-NEXT: [[VEC_SHUFFLE:%.*]] = shufflevector <2 x i32> [[X1]], <2 x i32> poison, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: ret <2 x i32> [[VEC_SHUFFLE]]
+;
+  %x1 = bitcast <8 x i8> %a0 to <2 x i32>
+  %vec.shuffle = shufflevector <2 x i32> %x1, <2 x i32> poison, <2 x i32> <i32 0, i32 1>
+  ret <2 x i32> %vec.shuffle
+}
+
+; negative - multiuse
+
+define <4 x i16> @unary_shuffle_sext_v8i8_v4i16_multiuse(<8 x i8> %a0, ptr %a1) {
+; CHECK-LABEL: define <4 x i16> @unary_shuffle_sext_v8i8_v4i16_multiuse(
+; CHECK-SAME: <8 x i8> [[A0:%.*]], ptr [[A1:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[X1:%.*]] = sext <8 x i8> [[A0]] to <8 x i16>
+; CHECK-NEXT: [[VEC_SHUFFLE:%.*]] = shufflevector <8 x i16> [[X1]], <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT: store <8 x i16> [[X1]], ptr [[A1]], align 16
+; CHECK-NEXT: ret <4 x i16> [[VEC_SHUFFLE]]
+;
+  %x1 = sext <8 x i8> %a0 to <8 x i16>
+  %vec.shuffle = shufflevector <8 x i16> %x1, <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  store <8 x i16> %x1, ptr %a1, align 16
+  ret <4 x i16> %vec.shuffle
+}