[llvm] ed51908 - [RISCV] Emit VP strided load in mgather combine. NFCI (#98112)

[via llvm-commits]

Author: Luke Lau
Date: 2024-07-09T14:57:21+08:00
New Revision: ed51908cec879c9dff435abdc70d8b03afc35c07

URL: https://github.com/llvm/llvm-project/commit/ed51908cec879c9dff435abdc70d8b03afc35c07
DIFF: https://github.com/llvm/llvm-project/commit/ed51908cec879c9dff435abdc70d8b03afc35c07.diff

LOG: [RISCV] Emit VP strided load in mgather combine. NFCI (#98112)

This combine is a duplication of the transform in
RISCVGatherScatterLowering but at the SelectionDAG level, so similarly
to #98111 we can replace the use of riscv_masked_strided_load with a VP
strided load.

Unlike #98111 we don't require #97800 or #97798 since it only operates
on fixed vectors with a non-zero stride.

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 74b2f8cb50d25..e2b6a98bc72ff 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -17062,15 +17062,16 @@ SDValue RISCVTargetLowering::PerformDAGCombine(SDNode *N,
         SDValue BasePtr = DAG.getNode(ISD::ADD, DL, PtrVT, MGN->getBasePtr(),
                                       DAG.getConstant(Addend, DL, PtrVT));
 
-        SDVTList VTs = DAG.getVTList({VT, MVT::Other});
-        SDValue IntID =
-          DAG.getTargetConstant(Intrinsic::riscv_masked_strided_load, DL,
-                                XLenVT);
-        SDValue Ops[] =
-          {MGN->getChain(), IntID, MGN->getPassThru(), BasePtr,
-           DAG.getConstant(StepNumerator, DL, XLenVT), MGN->getMask()};
-        return DAG.getMemIntrinsicNode(ISD::INTRINSIC_W_CHAIN, DL, VTs,
-                                       Ops, VT, MGN->getMemOperand());
+        SDValue EVL = DAG.getElementCount(DL, Subtarget.getXLenVT(),
+                                          VT.getVectorElementCount());
+        SDValue StridedLoad =
+            DAG.getStridedLoadVP(VT, DL, MGN->getChain(), BasePtr,
+                                 DAG.getConstant(StepNumerator, DL, XLenVT),
+                                 MGN->getMask(), EVL, MGN->getMemOperand());
+        SDValue VPSelect = DAG.getNode(ISD::VP_SELECT, DL, VT, MGN->getMask(),
+                                       StridedLoad, MGN->getPassThru(), EVL);
+        return DAG.getMergeValues({VPSelect, SDValue(StridedLoad.getNode(), 1)},
+                                  DL);
       }
     }