[llvm] [X86] Use GFNI for LZCNT vXi8 ops (PR #141888)
Phoebe Wang via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 1 22:26:10 PDT 2025
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@@ -28998,6 +28998,35 @@ static SDValue LowerVectorCTLZ(SDValue Op, const SDLoc &DL,
assert(Subtarget.hasSSSE3() && "Expected SSSE3 support for PSHUFB");
return LowerVectorCTLZInRegLUT(Op, DL, Subtarget, DAG);
}
+static SDValue LowerVectorCTLZ_GFNI(SDValue Op, SelectionDAG &DAG,
+ const X86Subtarget &Subtarget) {
+ SDLoc dl(Op);
+ MVT VT = Op.getSimpleValueType();
+ SDValue Input = Op.getOperand(0);
+
+ if (!VT.isVector() || VT.getVectorElementType() != MVT::i8)
+ return SDValue();
+ SmallVector<SDValue, 16> MatrixVals;
+ for (unsigned i = 0; i < VT.getVectorNumElements(); ++i) {
+ uint8_t mask = 1 << (7 - (i % 8));
+ MatrixVals.push_back(DAG.getConstant(mask, dl, MVT::i8));
+ }
+
+ SDValue Matrix = DAG.getBuildVector(VT, dl, MatrixVals);
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phoebewang wrote:
Try some AI assistants?
https://github.com/llvm/llvm-project/pull/141888
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