================
@@ -1701,6 +1701,46 @@ lowerVECTOR_SHUFFLE_VSHUF4I(const SDLoc &DL,
ArrayRef<int> Mask, MVT VT,
DAG.getConstant(Imm, DL, GRLenVT));
}
+/// Lower VECTOR_SHUFFLE whose result is the reversed source vector.
+///
+/// It is possible to do optimization for VECTOR_SHUFFLE performing vector
+/// reverse whose mask likes:
+/// <7, 6, 5, 4, 3, 2, 1, 0>
+///
+/// When undef's appear in the mask they are treated as if they were whatever
+/// value is necessary in order to fit the above forms.
+static SDValue
+lowerVECTOR_SHUFFLE_IsReverse(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
+ SDValue V1, SelectionDAG &DAG,
+ const LoongArchSubtarget &Subtarget) {
+ // Only vectors with i8/i16 elements which cannot match other patterns
+ // directly needs to do this.
+ if (VT != MVT::v16i8 && VT != MVT::v8i16 && VT != MVT::v32i8 &&
+ VT != MVT::v16i16)
+ return SDValue();
+
+ int MaskSize = Mask.size();
+ for (int i = 0; i < MaskSize; ++i) {
----------------
tangaac wrote:
use `ShuffleVectorInst::isReverseMask`
https://github.com/llvm/llvm-project/pull/163151
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