[PATCH] D159287: [RISCV] Remove vmv_v_x_vl workaround for constant splat. NFC

[Luke Lau via Phabricator via llvm-commits]

luke created this revision.
luke added reviewers: craig.topper, reames.
Herald added subscribers: jobnoorman, asb, sunshaoce, pmatos, VincentWu, vkmr, frasercrmck, luismarques, apazos, sameer.abuasal, s.egerton, Jim, benna, psnobl, jocewei, PkmX, the_o, brucehoult, MartinMosbeck, rogfer01, edward-jones, zzheng, jrtc27, shiva0217, kito-cheng, niosHD, sabuasal, simoncook, johnrusso, rbar, hiraditya, arichardson.
Herald added a project: All.
luke requested review of this revision.
Herald added subscribers: llvm-commits, wangpc, eopXD, MaskRay.
Herald added a project: LLVM.

Now that DAG.getConstant uses splat_vector_parts if needed on RV32, we can use
it directly without having to manually lower to a vmv_v_x_vl.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159287

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp


Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -4283,31 +4283,16 @@
                                                                RotateVT))
     return SDValue();
 
-  // If we just create the shift amount with
-  //
-  // DAG.getConstant(RotateAmt, DL, RotateVT)
-  //
-  // then for e64 we get a weird bitcasted build_vector on RV32 that we're
-  // unable to detect as a splat during pattern matching. So directly lower it
-  // to a vmv.v.x which gets matched to vror.vi.
-  MVT ContainerVT = getContainerForFixedLengthVector(DAG, RotateVT, Subtarget);
-  SDValue VL =
-      getDefaultVLOps(RotateVT, ContainerVT, DL, DAG, Subtarget).second;
   SDValue Op = DAG.getBitcast(RotateVT, SVN->getOperand(0));
 
   SDValue Rotate;
   // A rotate of an i16 by 8 bits either direction is equivalent to a byteswap,
   // so canonicalize to vrev8.
-  if (RotateVT.getScalarType() == MVT::i16 && RotateAmt == 8) {
+  if (RotateVT.getScalarType() == MVT::i16 && RotateAmt == 8)
     Rotate = DAG.getNode(ISD::BSWAP, DL, RotateVT, Op);
-  } else {
-    SDValue RotateAmtSplat = DAG.getNode(
-        RISCVISD::VMV_V_X_VL, DL, ContainerVT, DAG.getUNDEF(ContainerVT),
-        DAG.getConstant(RotateAmt, DL, Subtarget.getXLenVT()), VL);
-    RotateAmtSplat =
-        convertFromScalableVector(RotateVT, RotateAmtSplat, DAG, Subtarget);
-    Rotate = DAG.getNode(ISD::ROTL, DL, RotateVT, Op, RotateAmtSplat);
-  }
+  else
+    Rotate = DAG.getNode(ISD::ROTL, DL, RotateVT, Op,
+                         DAG.getConstant(RotateAmt, DL, RotateVT));
 
   return DAG.getBitcast(VT, Rotate);
 }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D159287.555047.patch
Type: text/x-patch
Size: 1753 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230831/f914d8ac/attachment.bin>