/// This doesn't do any checks for the availability of instructions for blending
/// these values. It relies on the availability of the X86ISD::BLENDI pattern to
/// be matched in the backend with the type given. What it does check for is
-/// that the shuffle mask is in fact a blend.
+/// that the shuffle mask is a blend, or convertible into a blend with zero.
static SDValue lowerVectorShuffleAsBlend(SDLoc DL, MVT VT, SDValue V1,
- SDValue V2, ArrayRef<int> Mask,
+ SDValue V2, ArrayRef<int> Original,
const X86Subtarget *Subtarget,
SelectionDAG &DAG) {
+ bool V1IsZero = ISD::isBuildVectorAllZeros(V1.getNode());
+ bool V2IsZero = ISD::isBuildVectorAllZeros(V2.getNode());
+ SmallVector<int, 8> Mask(Original.begin(), Original.end());
+ SmallBitVector Zeroable = computeZeroableShuffleElements(Mask, V1, V2);
+ bool ForceV1Zero = false, ForceV2Zero = false;
+
+ // Attempt to generate the binary blend mask. If an input is zero then
+ // we can use any lane.
+ // TODO: generalize the zero matching to any scalar like isShuffleEquivalent.
unsigned BlendMask = 0;
for (int i = 0, Size = Mask.size(); i < Size; ++i) {
- if (Mask[i] >= Size) {
- if (Mask[i] != i + Size)
- return SDValue(); // Shuffled V2 input!
+ int M = Mask[i];
+ if (M < 0)
+ continue;
+ if (M == i)
+ continue;
+ if (M == i + Size) {
BlendMask |= 1u << i;
continue;
}
- if (Mask[i] >= 0 && Mask[i] != i)
- return SDValue(); // Shuffled V1 input!
+ if (Zeroable[i]) {
+ if (V1IsZero) {
+ ForceV1Zero = true;
+ Mask[i] = i;
+ continue;
+ }
+ if (V2IsZero) {
+ ForceV2Zero = true;
+ BlendMask |= 1u << i;
+ Mask[i] = i + Size;
+ continue;
+ }
+ }
+ return SDValue(); // Shuffled input!
}
+
+ // Create a REAL zero vector - ISD::isBuildVectorAllZeros allows UNDEFs.
+ if (ForceV1Zero)
+ V1 = getZeroVector(VT, Subtarget, DAG, DL);
+ if (ForceV2Zero)
+ V2 = getZeroVector(VT, Subtarget, DAG, DL);
+
+ auto ScaleBlendMask = [](unsigned BlendMask, int Size, int Scale) {
+ unsigned ScaledMask = 0;
+ for (int i = 0; i != Size; ++i)
+ if (BlendMask & (1u << i))
+ for (int j = 0; j != Scale; ++j)
+ ScaledMask |= 1u << (i * Scale + j);
+ return ScaledMask;
+ };
+
switch (VT.SimpleTy) {
case MVT::v2f64:
case MVT::v4f32:
if (Subtarget->hasAVX2()) {
// Scale the blend by the number of 32-bit dwords per element.
int Scale = VT.getScalarSizeInBits() / 32;
- BlendMask = 0;
- for (int i = 0, Size = Mask.size(); i < Size; ++i)
- if (Mask[i] >= Size)
- for (int j = 0; j < Scale; ++j)
- BlendMask |= 1u << (i * Scale + j);
-
+ BlendMask = ScaleBlendMask(BlendMask, Mask.size(), Scale);
MVT BlendVT = VT.getSizeInBits() > 128 ? MVT::v8i32 : MVT::v4i32;
V1 = DAG.getBitcast(BlendVT, V1);
V2 = DAG.getBitcast(BlendVT, V2);
// For integer shuffles we need to expand the mask and cast the inputs to
// v8i16s prior to blending.
int Scale = 8 / VT.getVectorNumElements();
- BlendMask = 0;
- for (int i = 0, Size = Mask.size(); i < Size; ++i)
- if (Mask[i] >= Size)
- for (int j = 0; j < Scale; ++j)
- BlendMask |= 1u << (i * Scale + j);
-
+ BlendMask = ScaleBlendMask(BlendMask, Mask.size(), Scale);
V1 = DAG.getBitcast(MVT::v8i16, V1);
V2 = DAG.getBitcast(MVT::v8i16, V2);
return DAG.getBitcast(VT,