================
@@ -2317,6 +2317,54 @@ static SDValue lowerVECTOR_SHUFFLE_XVPICKOD(const SDLoc
&DL, ArrayRef<int> Mask,
return DAG.getNode(LoongArchISD::VPICKOD, DL, VT, V2, V1);
}
+// Check if exactly one element of the Mask is replaced by 'Replaced', while
+// all other elements are either 'Base + i' or undef (-1). On success, return
+// the index of the replaced element. Otherwise, just return -1.
+static int checkReplaceOne(ArrayRef<int> Mask, int Base, int Replaced) {
+ int MaskSize = Mask.size();
+ int Idx = -1;
+ for (int i = 0; i < MaskSize; ++i) {
+ if (Mask[i] == Base + i || Mask[i] == -1)
+ continue;
+ if (Mask[i] != Replaced)
+ return -1;
+ if (Idx == -1)
+ Idx = i;
+ else
+ return -1;
+ }
+ return Idx;
+}
+
+/// Lower VECTOR_SHUFFLE into XVINSVE0 (if possible).
+static SDValue
+lowerVECTOR_SHUFFLE_XVINSVE0(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
+ SDValue V1, SDValue V2, SelectionDAG &DAG,
+ const LoongArchSubtarget &Subtarget) {
+ // LoongArch LASX only supports xvinsve0.{w/d}.
+ if (VT != MVT::v8i32 && VT != MVT::v8f32 && VT != MVT::v4i64 &&
+ VT != MVT::v4f64)
+ return SDValue();
+
+ MVT GRLenVT = Subtarget.getGRLenVT();
+ int MaskSize = Mask.size();
+ assert(MaskSize == (int)VT.getVectorNumElements() && "Unexpected mask size");
+
+ // Case 1: the lowest element of V2 replaces one element in V1.
+ int Idx = checkReplaceOne(Mask, 0, MaskSize);
+ if (Idx != -1)
+ return DAG.getNode(LoongArchISD::XVINSVE0, DL, VT, V1, V2,
+ DAG.getConstant(Idx, DL, GRLenVT));
+
+ // Case 2: the lowest element of V1 replaces one element in V2.
+ Idx = checkReplaceOne(Mask, MaskSize, 0);
----------------
heiher wrote:
The logic appears sound. Would it be worthwhile to handle both cases in a
single pass over the mask, rather than iterating it twice?
https://github.com/llvm/llvm-project/pull/160857
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