[llvm] 7a6d150 - [RISCV] Reorder insert_subvector and bitcast in getDeinterleaveShiftAndTrunc. (#127258)

[via llvm-commits]

Author: Craig Topper
Date: 2025-02-14T18:45:58-08:00
New Revision: 7a6d1508ce5c6d33233d250a9d006066e019d712

URL: https://github.com/llvm/llvm-project/commit/7a6d1508ce5c6d33233d250a9d006066e019d712
DIFF: https://github.com/llvm/llvm-project/commit/7a6d1508ce5c6d33233d250a9d006066e019d712.diff

LOG: [RISCV] Reorder insert_subvector and bitcast in getDeinterleaveShiftAndTrunc. (#127258)

Put the bitcast before the insert_subvector. It's more likely the insert
subvector can be combined with other nodes. The insert_subvector is only
needed sometimes, and I'm considering reusing this function which might
require pulling the insert_subvector out.

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index cd441638bac9e..6392ee13bef55 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -4660,10 +4660,10 @@ static SDValue getDeinterleaveShiftAndTrunc(const SDLoc &DL, MVT VT,
   SDValue Res = DAG.getNode(ISD::SRL, DL, WideSrcVT, Src,
                             DAG.getConstant(Shift, DL, WideSrcVT));
   Res = DAG.getNode(ISD::TRUNCATE, DL, ResVT, Res);
-  MVT IntVT = VT.changeVectorElementTypeToInteger();
-  Res = DAG.getNode(ISD::INSERT_SUBVECTOR, DL, IntVT, DAG.getUNDEF(IntVT), Res,
-                    DAG.getVectorIdxConstant(0, DL));
-  return DAG.getBitcast(VT, Res);
+  MVT CastVT = ResVT.changeVectorElementType(VT.getVectorElementType());
+  Res = DAG.getBitcast(CastVT, Res);
+  return DAG.getNode(ISD::INSERT_SUBVECTOR, DL, VT, DAG.getUNDEF(VT), Res,
+                     DAG.getVectorIdxConstant(0, DL));
 }
 
 // Lower the following shuffle to vslidedown.