Revert "[AArch64] Lower alias mask to a whilewr" (#120261)

Reverts llvm/llvm-project#100769

A bug in the lowering (the subtraction should be reversed) was found
after merging and it will all be replaced by #117007 anyway.

patch.cherry: true
patch.metadata.original_sha: 412e1af
patch.platforms: chromiumos
patch.version_range.from: 545094
patch.version_range.until: 560071

Change-Id: I30c54b4bffb063035f78103be901928cfe34e29b

Author: SamTebbs33

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -1529,7 +1529,6 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
       setOperationAction(ISD::VECREDUCE_AND, VT, Custom);
       setOperationAction(ISD::VECREDUCE_OR, VT, Custom);
       setOperationAction(ISD::VECREDUCE_XOR, VT, Custom);
-      setOperationAction(ISD::OR, VT, Custom);
 
       setOperationAction(ISD::SELECT_CC, VT, Expand);
       setOperationAction(ISD::INSERT_VECTOR_ELT, VT, Custom);
@@ -13940,128 +13939,8 @@ static SDValue tryLowerToSLI(SDNode *N, SelectionDAG &DAG) {
   return ResultSLI;
 }
 
-/// Try to lower the construction of a pointer alias mask to a WHILEWR.
-/// The mask's enabled lanes represent the elements that will not overlap across
-/// one loop iteration. This tries to match:
-/// or (splat (setcc_lt (sub ptrA, ptrB), -(element_size - 1))),
-///    (get_active_lane_mask 0, (div (sub ptrA, ptrB), element_size))
-SDValue tryWhileWRFromOR(SDValue Op, SelectionDAG &DAG,
-                         const AArch64Subtarget &Subtarget) {
-  if (!Subtarget.hasSVE2())
-    return SDValue();
-  SDValue LaneMask = Op.getOperand(0);
-  SDValue Splat = Op.getOperand(1);
-
-  if (Splat.getOpcode() != ISD::SPLAT_VECTOR)
-    std::swap(LaneMask, Splat);
-
-  if (LaneMask.getOpcode() != ISD::INTRINSIC_WO_CHAIN ||
-      LaneMask.getConstantOperandVal(0) != Intrinsic::get_active_lane_mask ||
-      Splat.getOpcode() != ISD::SPLAT_VECTOR)
-    return SDValue();
-
-  SDValue Cmp = Splat.getOperand(0);
-  if (Cmp.getOpcode() != ISD::SETCC)
-    return SDValue();
-
-  CondCodeSDNode *Cond = cast<CondCodeSDNode>(Cmp.getOperand(2));
-
-  auto ComparatorConst = dyn_cast<ConstantSDNode>(Cmp.getOperand(1));
-  if (!ComparatorConst || ComparatorConst->getSExtValue() > 0 ||
-      Cond->get() != ISD::CondCode::SETLT)
-    return SDValue();
-  unsigned CompValue = std::abs(ComparatorConst->getSExtValue());
-  unsigned EltSize = CompValue + 1;
-  if (!isPowerOf2_64(EltSize) || EltSize > 8)
-    return SDValue();
-
-  SDValue Diff = Cmp.getOperand(0);
-  if (Diff.getOpcode() != ISD::SUB || Diff.getValueType() != MVT::i64)
-    return SDValue();
-
-  if (!isNullConstant(LaneMask.getOperand(1)) ||
-      (EltSize != 1 && LaneMask.getOperand(2).getOpcode() != ISD::SRA))
-    return SDValue();
-
-  // The number of elements that alias is calculated by dividing the positive
-  // difference between the pointers by the element size. An alias mask for i8
-  // elements omits the division because it would just divide by 1
-  if (EltSize > 1) {
-    SDValue DiffDiv = LaneMask.getOperand(2);
-    auto DiffDivConst = dyn_cast<ConstantSDNode>(DiffDiv.getOperand(1));
-    if (!DiffDivConst || DiffDivConst->getZExtValue() != Log2_64(EltSize))
-      return SDValue();
-    if (EltSize > 2) {
-      // When masking i32 or i64 elements, the positive value of the
-      // possibly-negative difference comes from a select of the difference if
-      // it's positive, otherwise the difference plus the element size if it's
-      // negative: pos_diff = diff < 0 ? (diff + 7) : diff
-      SDValue Select = DiffDiv.getOperand(0);
-      // Make sure the difference is being compared by the select
-      if (Select.getOpcode() != ISD::SELECT_CC || Select.getOperand(3) != Diff)
-        return SDValue();
-      // Make sure it's checking if the difference is less than 0
-      if (!isNullConstant(Select.getOperand(1)) ||
-          cast<CondCodeSDNode>(Select.getOperand(4))->get() !=
-              ISD::CondCode::SETLT)
-        return SDValue();
-      // An add creates a positive value from the negative difference
-      SDValue Add = Select.getOperand(2);
-      if (Add.getOpcode() != ISD::ADD || Add.getOperand(0) != Diff)
-        return SDValue();
-      if (auto *AddConst = dyn_cast<ConstantSDNode>(Add.getOperand(1));
-          !AddConst || AddConst->getZExtValue() != EltSize - 1)
-        return SDValue();
-    } else {
-      // When masking i16 elements, this positive value comes from adding the
-      // difference's sign bit to the difference itself. This is equivalent to
-      // the 32 bit and 64 bit case: pos_diff = diff + sign_bit (diff)
-      SDValue Add = DiffDiv.getOperand(0);
-      if (Add.getOpcode() != ISD::ADD || Add.getOperand(0) != Diff)
-        return SDValue();
-      // A logical right shift by 63 extracts the sign bit from the difference
-      SDValue Shift = Add.getOperand(1);
-      if (Shift.getOpcode() != ISD::SRL || Shift.getOperand(0) != Diff)
-        return SDValue();
-      if (auto *ShiftConst = dyn_cast<ConstantSDNode>(Shift.getOperand(1));
-          !ShiftConst || ShiftConst->getZExtValue() != 63)
-        return SDValue();
-    }
-  } else if (LaneMask.getOperand(2) != Diff)
-    return SDValue();
-
-  SDValue StorePtr = Diff.getOperand(0);
-  SDValue ReadPtr = Diff.getOperand(1);
-
-  unsigned IntrinsicID = 0;
-  switch (EltSize) {
-  case 1:
-    IntrinsicID = Intrinsic::aarch64_sve_whilewr_b;
-    break;
-  case 2:
-    IntrinsicID = Intrinsic::aarch64_sve_whilewr_h;
-    break;
-  case 4:
-    IntrinsicID = Intrinsic::aarch64_sve_whilewr_s;
-    break;
-  case 8:
-    IntrinsicID = Intrinsic::aarch64_sve_whilewr_d;
-    break;
-  default:
-    return SDValue();
-  }
-  SDLoc DL(Op);
-  SDValue ID = DAG.getConstant(IntrinsicID, DL, MVT::i32);
-  return DAG.getNode(ISD::INTRINSIC_WO_CHAIN, DL, Op.getValueType(), ID,
-                     StorePtr, ReadPtr);
-}
-
 SDValue AArch64TargetLowering::LowerVectorOR(SDValue Op,
                                              SelectionDAG &DAG) const {
-  if (SDValue SV =
-          tryWhileWRFromOR(Op, DAG, DAG.getSubtarget<AArch64Subtarget>()))
-    return SV;
-
   if (useSVEForFixedLengthVectorVT(Op.getValueType(),
                                    !Subtarget->isNeonAvailable()))
     return LowerToScalableOp(Op, DAG);