[AArch64] Don't use LowerToPredicatedOp to shufflevector -> SVE lowerings

The use of `LowerToPredicatedOp` here seems like a mistake as
`LowerToPredicatedOp` turns the SDValue passed to it into the desired
predicated node by copying over operands (and adding a predicate). This
results in two odd things here, the BITCASTs created and passed to
`LowerToPredicatedOp` are not used, only the operands of those bitcasts
are taken. Secondly, when a shuffle vector node is passed directly to
`LowerToPredicatedOp` to create a `REVD_MERGE_PASSTHRU` node
an invalid REV node is created as REV only takes one vector operand,
but both operands from the shuffle vector are copied to the new REV node.
This is not an issue in practice as the extra operand is ignored.

These issues were found by the verification added in #140472.

Part of #140472.

Note: Test changes only result in the vxi64 lowering matching the vxf64
lowering.

Author: MacDue

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -29773,36 +29773,35 @@ SDValue AArch64TargetLowering::LowerFixedLengthVECTOR_SHUFFLEToSVE(
     return convertFromScalableVector(DAG, VT, Op);
   }
 
+  auto lowerToRevMergePassthru = [&](unsigned Opcode, SDValue Vec, EVT NewVT) {
+    auto Pg = getPredicateForVector(DAG, DL, NewVT);
+    SDValue RevOp = DAG.getNode(ISD::BITCAST, DL, NewVT, Vec);
+    auto Rev =
+        DAG.getNode(Opcode, DL, NewVT, Pg, RevOp, DAG.getUNDEF(ContainerVT));
+    auto Cast = DAG.getNode(ISD::BITCAST, DL, ContainerVT, Rev);
+    return convertFromScalableVector(DAG, VT, Cast);
+  };
+
   unsigned EltSize = VT.getScalarSizeInBits();
   for (unsigned LaneSize : {64U, 32U, 16U}) {
     if (isREVMask(ShuffleMask, EltSize, VT.getVectorNumElements(), LaneSize)) {
-      EVT NewVT =
-          getPackedSVEVectorVT(EVT::getIntegerVT(*DAG.getContext(), LaneSize));
       unsigned RevOp;
       if (EltSize == 8)
         RevOp = AArch64ISD::BSWAP_MERGE_PASSTHRU;
       else if (EltSize == 16)
         RevOp = AArch64ISD::REVH_MERGE_PASSTHRU;
       else
         RevOp = AArch64ISD::REVW_MERGE_PASSTHRU;
-
-      Op = DAG.getNode(ISD::BITCAST, DL, NewVT, Op1);
-      Op = LowerToPredicatedOp(Op, DAG, RevOp);
-      Op = DAG.getNode(ISD::BITCAST, DL, ContainerVT, Op);
-      return convertFromScalableVector(DAG, VT, Op);
+      EVT NewVT =
+          getPackedSVEVectorVT(EVT::getIntegerVT(*DAG.getContext(), LaneSize));
+      return lowerToRevMergePassthru(RevOp, Op1, NewVT);
     }
   }
 
   if (Subtarget->hasSVE2p1() && EltSize == 64 &&
       isREVMask(ShuffleMask, EltSize, VT.getVectorNumElements(), 128)) {
-    if (!VT.isFloatingPoint())
-      return LowerToPredicatedOp(Op, DAG, AArch64ISD::REVD_MERGE_PASSTHRU);
-
-    EVT NewVT = getPackedSVEVectorVT(EVT::getIntegerVT(*DAG.getContext(), 64));
-    Op = DAG.getNode(ISD::BITCAST, DL, NewVT, Op1);
-    Op = LowerToPredicatedOp(Op, DAG, AArch64ISD::REVD_MERGE_PASSTHRU);
-    Op = DAG.getNode(ISD::BITCAST, DL, ContainerVT, Op);
-    return convertFromScalableVector(DAG, VT, Op);
+    return lowerToRevMergePassthru(AArch64ISD::REVD_MERGE_PASSTHRU, Op1,
+                                   ContainerVT);
   }
 
   unsigned WhichResult;

llvm/test/CodeGen/AArch64/sve-fixed-length-permute-rev.ll

@@ -213,8 +213,9 @@ define void @test_revdv4i64_sve2p1(ptr %a) #2 {
 ; CHECK-LABEL: test_revdv4i64_sve2p1:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    ptrue p0.d, vl4
+; CHECK-NEXT:    ptrue p1.d
 ; CHECK-NEXT:    ld1d { z0.d }, p0/z, [x0]
-; CHECK-NEXT:    revd z0.q, p0/m, z0.q
+; CHECK-NEXT:    revd z0.q, p1/m, z0.q
 ; CHECK-NEXT:    st1d { z0.d }, p0, [x0]
 ; CHECK-NEXT:    ret
   %tmp1 = load <4 x i64>, ptr %a

llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-permute-rev.ll

@@ -677,7 +677,7 @@ define void @test_revdv4i64_sve2p1(ptr %a) #1 {
 ; CHECK-LABEL: test_revdv4i64_sve2p1:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    ldp q0, q1, [x0]
-; CHECK-NEXT:    ptrue p0.d, vl2
+; CHECK-NEXT:    ptrue p0.d
 ; CHECK-NEXT:    revd z0.q, p0/m, z0.q
 ; CHECK-NEXT:    revd z1.q, p0/m, z1.q
 ; CHECK-NEXT:    stp q0, q1, [x0]
@@ -686,7 +686,7 @@ define void @test_revdv4i64_sve2p1(ptr %a) #1 {
 ; NONEON-NOSVE-LABEL: test_revdv4i64_sve2p1:
 ; NONEON-NOSVE:       // %bb.0:
 ; NONEON-NOSVE-NEXT:    ldp q0, q1, [x0]
-; NONEON-NOSVE-NEXT:    ptrue p0.d, vl2
+; NONEON-NOSVE-NEXT:    ptrue p0.d
 ; NONEON-NOSVE-NEXT:    revd z0.q, p0/m, z0.q
 ; NONEON-NOSVE-NEXT:    revd z1.q, p0/m, z1.q
 ; NONEON-NOSVE-NEXT:    stp q0, q1, [x0]