[llvm] [VP][RISCV] Add vp.cttz.elts intrinsic and its RISC-V codegen (PR #90502)

[Min-Yih Hsu via llvm-commits]

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@@ -5341,6 +5344,45 @@ RISCVTargetLowering::lowerCTLZ_CTTZ_ZERO_UNDEF(SDValue Op,
   return Res;
 }
 
+SDValue RISCVTargetLowering::lowerVPCttzElements(SDValue Op,
+                                                 SelectionDAG &DAG) const {
+  SDLoc DL(Op);
+  MVT XLenVT = Subtarget.getXLenVT();
+  SDValue Source = Op->getOperand(0);
+  MVT SrcVT = Source.getSimpleValueType();
+  SDValue Mask = Op->getOperand(1);
+  SDValue EVL = Op->getOperand(2);
+
+  if (SrcVT.isFixedLengthVector()) {
+    MVT ContainerVT = getContainerForFixedLengthVector(SrcVT);
+    Source = convertToScalableVector(ContainerVT, Source, DAG, Subtarget);
+    Mask = convertToScalableVector(getMaskTypeFor(ContainerVT), Mask, DAG,
+                                   Subtarget);
+    SrcVT = ContainerVT;
+  }
+
+  // Convert to boolean vector.
+  if (SrcVT.getScalarType() != MVT::i1) {
+    SDValue AllZero = DAG.getConstant(0, DL, SrcVT);
+    SrcVT = MVT::getVectorVT(MVT::i1, SrcVT.getVectorElementCount());
+    Source = DAG.getNode(RISCVISD::SETCC_VL, DL, SrcVT,
+                         {Source, AllZero, DAG.getCondCode(ISD::SETNE),
+                          DAG.getUNDEF(SrcVT), Mask, EVL});
+  }
+
+  SDValue Res = DAG.getNode(RISCVISD::VFIRST_VL, DL, XLenVT, Source, Mask, EVL);
+  if (Op->getOpcode() == ISD::VP_CTTZ_ELTS_ZERO_UNDEF)
+    // In this case, we can interpret poison as -1, so nothing to do further.
+    return Res;
+
+  // Convert -1 to VL.
+  SDValue SetCC =
+      DAG.getSetCC(DL, XLenVT, Res, DAG.getConstant(0, DL, XLenVT), ISD::SETLT);
+  Res = DAG.getSelect(DL, XLenVT, SetCC, DAG.getZExtOrTrunc(EVL, DL, XLenVT),
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mshockwave wrote:

Fixed.

https://github.com/llvm/llvm-project/pull/90502