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-rw-r--r--llvm/lib/Target/X86/X86ISelLowering.cpp40
1 files changed, 39 insertions, 1 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index d00b09e71d1..a07718b9bd8 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -7438,6 +7438,37 @@ static SDValue getV4X86ShuffleImm8ForMask(ArrayRef<int> Mask,
return DAG.getConstant(Imm, MVT::i8);
}
+/// \brief Try to emit a blend instruction for a shuffle using bit math.
+///
+/// This is used as a fallback approach when first class blend instructions are
+/// unavailable. Currently it is only suitable for integer vectors, but could
+/// be generalized for floating point vectors if desirable.
+static SDValue lowerVectorShuffleAsBitBlend(SDLoc DL, MVT VT, SDValue V1,
+ SDValue V2, ArrayRef<int> Mask,
+ SelectionDAG &DAG) {
+ assert(VT.isInteger() && "Only supports integer vector types!");
+ MVT EltVT = VT.getScalarType();
+ int NumEltBits = EltVT.getSizeInBits();
+ SDValue Zero = DAG.getConstant(0, EltVT);
+ SDValue AllOnes = DAG.getConstant(APInt::getAllOnesValue(NumEltBits), EltVT);
+ SmallVector<SDValue, 16> MaskOps;
+ for (int i = 0, Size = Mask.size(); i < Size; ++i) {
+ if (Mask[i] != -1 && Mask[i] != i && Mask[i] != i + Size)
+ return SDValue(); // Shuffled input!
+ MaskOps.push_back(Mask[i] < Size ? AllOnes : Zero);
+ }
+
+ SDValue V1Mask = DAG.getNode(ISD::BUILD_VECTOR, DL, VT, MaskOps);
+ V1 = DAG.getNode(ISD::AND, DL, VT, V1, V1Mask);
+ // We have to cast V2 around.
+ MVT MaskVT = MVT::getVectorVT(MVT::i64, VT.getSizeInBits() / 64);
+ V2 = DAG.getNode(ISD::BITCAST, DL, VT,
+ DAG.getNode(X86ISD::ANDNP, DL, MaskVT,
+ DAG.getNode(ISD::BITCAST, DL, MaskVT, V1Mask),
+ DAG.getNode(ISD::BITCAST, DL, MaskVT, V2)));
+ return DAG.getNode(ISD::OR, DL, VT, V1, V2);
+}
+
/// \brief Try to emit a blend instruction for a shuffle.
///
/// This doesn't do any checks for the availability of instructions for blending
@@ -7448,7 +7479,6 @@ static SDValue lowerVectorShuffleAsBlend(SDLoc DL, MVT VT, SDValue V1,
SDValue V2, ArrayRef<int> Mask,
const X86Subtarget *Subtarget,
SelectionDAG &DAG) {
-
unsigned BlendMask = 0;
for (int i = 0, Size = Mask.size(); i < Size; ++i) {
if (Mask[i] >= Size) {
@@ -9667,6 +9697,10 @@ static SDValue lowerV8I16VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
DL, MVT::v8i16, V1, V2, Mask, Subtarget, DAG))
return Rotate;
+ if (SDValue BitBlend =
+ lowerVectorShuffleAsBitBlend(DL, MVT::v8i16, V1, V2, Mask, DAG))
+ return BitBlend;
+
if (NumV1Inputs + NumV2Inputs <= 4)
return lowerV8I16BasicBlendVectorShuffle(DL, V1, V2, Mask, Subtarget, DAG);
@@ -10034,6 +10068,10 @@ static SDValue lowerV16I8VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
Mask, Subtarget, DAG))
return V;
+ if (SDValue BitBlend =
+ lowerVectorShuffleAsBitBlend(DL, MVT::v16i8, V1, V2, Mask, DAG))
+ return BitBlend;
+
// Check whether a compaction lowering can be done. This handles shuffles
// which take every Nth element for some even N. See the helper function for
// details.
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