[llvm] 6942927 - [DAG] combineConcatVectorOfScalars - stop always creating UNDEF nodes. NFC.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2024-03-21T16:37:48Z
New Revision: 69429276098df2f2cf67dcab1c96ce8f56280c11

URL: https://github.com/llvm/llvm-project/commit/69429276098df2f2cf67dcab1c96ce8f56280c11
DIFF: https://github.com/llvm/llvm-project/commit/69429276098df2f2cf67dcab1c96ce8f56280c11.diff

LOG: [DAG] combineConcatVectorOfScalars - stop always creating UNDEF nodes. NFC.

Noticed in debug logs - most calls to visitVECTOR_SHUFFLE resulted into wasteful UNDEF node creations, despite almost never being used.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c83793d15b2ece..7009f375df1151 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -23447,9 +23447,7 @@ static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
   SDLoc DL(N);
   EVT VT = N->getValueType(0);
   SmallVector<SDValue, 8> Ops;
-
   EVT SVT = EVT::getIntegerVT(*DAG.getContext(), OpVT.getSizeInBits());
-  SDValue ScalarUndef = DAG.getNode(ISD::UNDEF, DL, SVT);
 
   // Keep track of what we encounter.
   bool AnyInteger = false;
@@ -23459,7 +23457,7 @@ static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
         !Op.getOperand(0).getValueType().isVector())
       Ops.push_back(Op.getOperand(0));
     else if (ISD::UNDEF == Op.getOpcode())
-      Ops.push_back(ScalarUndef);
+      Ops.push_back(DAG.getNode(ISD::UNDEF, DL, SVT));
     else
       return SDValue();
 
@@ -23479,13 +23477,12 @@ static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
   // Replace UNDEFs by another scalar UNDEF node, of the final desired type.
   if (AnyFP) {
     SVT = EVT::getFloatingPointVT(OpVT.getSizeInBits());
-    ScalarUndef = DAG.getNode(ISD::UNDEF, DL, SVT);
     if (AnyInteger) {
       for (SDValue &Op : Ops) {
         if (Op.getValueType() == SVT)
           continue;
         if (Op.isUndef())
-          Op = ScalarUndef;
+          Op = DAG.getNode(ISD::UNDEF, DL, SVT);
         else
           Op = DAG.getBitcast(SVT, Op);
       }