[llvm] [AArch64] Remove dead vector.partial.reduce DAGCombine (NFC) (PR #159362)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Gaëtan Bossu (gbossu)

<details>
<summary>Changes</summary>

This intrinsic is already lowered in SelectionDAGBuilder.cpp into ISD::PARTIAL_REDUCE_UMLA, so the DAGCombine will never trigger. The optimisations we were doing are also superseded by generic ones in DAGCombiner.cpp.

---
Full diff: https://github.com/llvm/llvm-project/pull/159362.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/AArch64ISelLowering.cpp (-143) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 0ca5e89263b72..0d64f062df39e 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -22515,138 +22515,6 @@ static SDValue convertMergedOpToPredOp(SDNode *N, unsigned Opc,
   return SDValue();
 }
 
-SDValue tryLowerPartialReductionToDot(SDNode *N,
-                                      const AArch64Subtarget *Subtarget,
-                                      SelectionDAG &DAG) {
-
-  assert(N->getOpcode() == ISD::INTRINSIC_WO_CHAIN &&
-         getIntrinsicID(N) == Intrinsic::vector_partial_reduce_add &&
-         "Expected a partial reduction node");
-
-  bool Scalable = N->getValueType(0).isScalableVector();
-  if (Scalable && !Subtarget->isSVEorStreamingSVEAvailable())
-    return SDValue();
-  if (!Scalable && (!Subtarget->isNeonAvailable() || !Subtarget->hasDotProd()))
-    return SDValue();
-
-  SDLoc DL(N);
-
-  SDValue Op2 = N->getOperand(2);
-  unsigned Op2Opcode = Op2->getOpcode();
-  SDValue MulOpLHS, MulOpRHS;
-  bool MulOpLHSIsSigned, MulOpRHSIsSigned;
-  if (ISD::isExtOpcode(Op2Opcode)) {
-    MulOpLHSIsSigned = MulOpRHSIsSigned = (Op2Opcode == ISD::SIGN_EXTEND);
-    MulOpLHS = Op2->getOperand(0);
-    MulOpRHS = DAG.getConstant(1, DL, MulOpLHS.getValueType());
-  } else if (Op2Opcode == ISD::MUL) {
-    SDValue ExtMulOpLHS = Op2->getOperand(0);
-    SDValue ExtMulOpRHS = Op2->getOperand(1);
-
-    unsigned ExtMulOpLHSOpcode = ExtMulOpLHS->getOpcode();
-    unsigned ExtMulOpRHSOpcode = ExtMulOpRHS->getOpcode();
-    if (!ISD::isExtOpcode(ExtMulOpLHSOpcode) ||
-        !ISD::isExtOpcode(ExtMulOpRHSOpcode))
-      return SDValue();
-
-    MulOpLHSIsSigned = ExtMulOpLHSOpcode == ISD::SIGN_EXTEND;
-    MulOpRHSIsSigned = ExtMulOpRHSOpcode == ISD::SIGN_EXTEND;
-
-    MulOpLHS = ExtMulOpLHS->getOperand(0);
-    MulOpRHS = ExtMulOpRHS->getOperand(0);
-
-    if (MulOpLHS.getValueType() != MulOpRHS.getValueType())
-      return SDValue();
-  } else
-    return SDValue();
-
-  SDValue Acc = N->getOperand(1);
-  EVT ReducedVT = N->getValueType(0);
-  EVT MulSrcVT = MulOpLHS.getValueType();
-
-  // Dot products operate on chunks of four elements so there must be four times
-  // as many elements in the wide type
-  if (!(ReducedVT == MVT::nxv4i64 && MulSrcVT == MVT::nxv16i8) &&
-      !(ReducedVT == MVT::nxv4i32 && MulSrcVT == MVT::nxv16i8) &&
-      !(ReducedVT == MVT::nxv2i64 && MulSrcVT == MVT::nxv8i16) &&
-      !(ReducedVT == MVT::v4i64 && MulSrcVT == MVT::v16i8) &&
-      !(ReducedVT == MVT::v4i32 && MulSrcVT == MVT::v16i8) &&
-      !(ReducedVT == MVT::v2i32 && MulSrcVT == MVT::v8i8))
-    return SDValue();
-
-  // If the extensions are mixed, we should lower it to a usdot instead
-  unsigned Opcode = 0;
-  if (MulOpLHSIsSigned != MulOpRHSIsSigned) {
-    if (!Subtarget->hasMatMulInt8())
-      return SDValue();
-
-    bool Scalable = N->getValueType(0).isScalableVT();
-    // There's no nxv2i64 version of usdot
-    if (Scalable && ReducedVT != MVT::nxv4i32 && ReducedVT != MVT::nxv4i64)
-      return SDValue();
-
-    Opcode = AArch64ISD::USDOT;
-    // USDOT expects the signed operand to be last
-    if (!MulOpRHSIsSigned)
-      std::swap(MulOpLHS, MulOpRHS);
-  } else
-    Opcode = MulOpLHSIsSigned ? AArch64ISD::SDOT : AArch64ISD::UDOT;
-
-  // Partial reduction lowering for (nx)v16i8 to (nx)v4i64 requires an i32 dot
-  // product followed by a zero / sign extension
-  if ((ReducedVT == MVT::nxv4i64 && MulSrcVT == MVT::nxv16i8) ||
-      (ReducedVT == MVT::v4i64 && MulSrcVT == MVT::v16i8)) {
-    EVT ReducedVTI32 =
-        (ReducedVT.isScalableVector()) ? MVT::nxv4i32 : MVT::v4i32;
-
-    SDValue DotI32 =
-        DAG.getNode(Opcode, DL, ReducedVTI32,
-                    DAG.getConstant(0, DL, ReducedVTI32), MulOpLHS, MulOpRHS);
-    SDValue Extended = DAG.getSExtOrTrunc(DotI32, DL, ReducedVT);
-    return DAG.getNode(ISD::ADD, DL, ReducedVT, Acc, Extended);
-  }
-
-  return DAG.getNode(Opcode, DL, ReducedVT, Acc, MulOpLHS, MulOpRHS);
-}
-
-SDValue tryLowerPartialReductionToWideAdd(SDNode *N,
-                                          const AArch64Subtarget *Subtarget,
-                                          SelectionDAG &DAG) {
-
-  assert(N->getOpcode() == ISD::INTRINSIC_WO_CHAIN &&
-         getIntrinsicID(N) == Intrinsic::vector_partial_reduce_add &&
-         "Expected a partial reduction node");
-
-  if (!Subtarget->hasSVE2() && !Subtarget->isStreamingSVEAvailable())
-    return SDValue();
-
-  SDLoc DL(N);
-
-  if (!ISD::isExtOpcode(N->getOperand(2).getOpcode()))
-    return SDValue();
-  SDValue Acc = N->getOperand(1);
-  SDValue Ext = N->getOperand(2);
-  EVT AccVT = Acc.getValueType();
-  EVT ExtVT = Ext.getValueType();
-  if (ExtVT.getVectorElementType() != AccVT.getVectorElementType())
-    return SDValue();
-
-  SDValue ExtOp = Ext->getOperand(0);
-  EVT ExtOpVT = ExtOp.getValueType();
-
-  if (!(ExtOpVT == MVT::nxv4i32 && AccVT == MVT::nxv2i64) &&
-      !(ExtOpVT == MVT::nxv8i16 && AccVT == MVT::nxv4i32) &&
-      !(ExtOpVT == MVT::nxv16i8 && AccVT == MVT::nxv8i16))
-    return SDValue();
-
-  bool ExtOpIsSigned = Ext.getOpcode() == ISD::SIGN_EXTEND;
-  unsigned BottomOpcode =
-      ExtOpIsSigned ? AArch64ISD::SADDWB : AArch64ISD::UADDWB;
-  unsigned TopOpcode = ExtOpIsSigned ? AArch64ISD::SADDWT : AArch64ISD::UADDWT;
-  SDValue BottomNode = DAG.getNode(BottomOpcode, DL, AccVT, Acc, ExtOp);
-  return DAG.getNode(TopOpcode, DL, AccVT, BottomNode, ExtOp);
-}
-
 static SDValue combineSVEBitSel(unsigned IID, SDNode *N, SelectionDAG &DAG) {
   SDLoc DL(N);
   EVT VT = N->getValueType(0);
@@ -22679,17 +22547,6 @@ static SDValue performIntrinsicCombine(SDNode *N,
   switch (IID) {
   default:
     break;
-  case Intrinsic::vector_partial_reduce_add: {
-    if (SDValue Dot = tryLowerPartialReductionToDot(N, Subtarget, DAG))
-      return Dot;
-    if (SDValue WideAdd = tryLowerPartialReductionToWideAdd(N, Subtarget, DAG))
-      return WideAdd;
-    SDLoc DL(N);
-    SDValue Input = N->getOperand(2);
-    return DAG.getNode(ISD::PARTIAL_REDUCE_UMLA, DL, N->getValueType(0),
-                       N->getOperand(1), Input,
-                       DAG.getConstant(1, DL, Input.getValueType()));
-  }
   case Intrinsic::aarch64_neon_vcvtfxs2fp:
   case Intrinsic::aarch64_neon_vcvtfxu2fp:
     return tryCombineFixedPointConvert(N, DCI, DAG);

``````````

</details>


https://github.com/llvm/llvm-project/pull/159362