[llvm] Remove `NVPTXTargetLowering::LowerCONCAT_VECTORS` (PR #133145)

[Ethan Kaji via llvm-commits]

https://github.com/Esan5 created https://github.com/llvm/llvm-project/pull/133145

>From #120030, `NVPTXTargetLowering::LowerCONCAT_VECTORS` is actually dead code since https://github.com/llvm/llvm-project/commit/be8dc6499ac00b2e5a608dbcec3ecb17348299e0.

This PR removes code from NVPTX, though it will still be ported to SelectionDAG.

>From a5389387d1669e7374562cc948a0b7b075f9250f Mon Sep 17 00:00:00 2001
From: Ethan Kaji <ethan.kaji at gmail.com>
Date: Wed, 26 Mar 2025 15:34:16 -0400
Subject: [PATCH] remove dead concat vector code from nvptx

---
 llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp | 24 ---------------------
 llvm/lib/Target/NVPTX/NVPTXISelLowering.h   |  1 -
 2 files changed, 25 deletions(-)

diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
index 3e755c25fd91a..f6793d53967b1 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -2110,28 +2110,6 @@ SDValue NVPTXTargetLowering::LowerSTACKSAVE(SDValue Op,
   return DAG.getMergeValues({ASC, SDValue(SS.getNode(), 1)}, DL);
 }
 
-// By default CONCAT_VECTORS is lowered by ExpandVectorBuildThroughStack()
-// (see LegalizeDAG.cpp). This is slow and uses local memory.
-// We use extract/insert/build vector just as what LegalizeOp() does in llvm 2.5
-SDValue
-NVPTXTargetLowering::LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) const {
-  SDNode *Node = Op.getNode();
-  SDLoc dl(Node);
-  SmallVector<SDValue, 8> Ops;
-  unsigned NumOperands = Node->getNumOperands();
-  for (unsigned i = 0; i < NumOperands; ++i) {
-    SDValue SubOp = Node->getOperand(i);
-    EVT VVT = SubOp.getNode()->getValueType(0);
-    EVT EltVT = VVT.getVectorElementType();
-    unsigned NumSubElem = VVT.getVectorNumElements();
-    for (unsigned j = 0; j < NumSubElem; ++j) {
-      Ops.push_back(DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, EltVT, SubOp,
-                                DAG.getIntPtrConstant(j, dl)));
-    }
-  }
-  return DAG.getBuildVector(Node->getValueType(0), dl, Ops);
-}
-
 SDValue NVPTXTargetLowering::LowerBITCAST(SDValue Op, SelectionDAG &DAG) const {
   // Handle bitcasting from v2i8 without hitting the default promotion
   // strategy which goes through stack memory.
@@ -2777,8 +2755,6 @@ NVPTXTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
     return LowerINSERT_VECTOR_ELT(Op, DAG);
   case ISD::VECTOR_SHUFFLE:
     return LowerVECTOR_SHUFFLE(Op, DAG);
-  case ISD::CONCAT_VECTORS:
-    return LowerCONCAT_VECTORS(Op, DAG);
   case ISD::STORE:
     return LowerSTORE(Op, DAG);
   case ISD::LOAD:
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
index f41c569a65544..f8c17d7118bbb 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
@@ -279,7 +279,6 @@ class NVPTXTargetLowering : public TargetLowering {
   SDValue LowerBITCAST(SDValue Op, SelectionDAG &DAG) const;
 
   SDValue LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const;
-  SDValue LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const;