[X86][AVX] combineConcatVectorOps - use getBROADCAST_LOAD helper for splat of normal vector loads. NFCI.

Reapplied from rG1cfecf4fc427 with fix for PR51226 - ensure the load is a normal (non-ext) load.

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -51665,9 +51665,11 @@ static SDValue combineConcatVectorOps(const SDLoc &DL, MVT VT,
     if (Op0.getOpcode() == X86ISD::VBROADCAST)
       return DAG.getNode(Op0.getOpcode(), DL, VT, Op0.getOperand(0));
 
-    // If this scalar/subvector broadcast_load is inserted into both halves, use
-    // a larger broadcast_load. Update other uses to use an extracted subvector.
-    if (Op0.getOpcode() == X86ISD::VBROADCAST_LOAD ||
+    // If this simple subvector or scalar/subvector broadcast_load is inserted
+    // into both halves, use a larger broadcast_load. Update other uses to use
+    // an extracted subvector.
+    if (ISD::isNormalLoad(Op0.getNode()) ||
+        Op0.getOpcode() == X86ISD::VBROADCAST_LOAD ||
         Op0.getOpcode() == X86ISD::SUBV_BROADCAST_LOAD) {
       auto *Mem = cast<MemSDNode>(Op0);
       unsigned Opc = Op0.getOpcode() == X86ISD::VBROADCAST_LOAD
@@ -51682,24 +51684,6 @@ static SDValue combineConcatVectorOps(const SDLoc &DL, MVT VT,
       }
     }
 
-    // If this is a simple subvector load repeated across multiple lanes, then
-    // broadcast the load. Update other uses to use an extracted subvector.
-    if (auto *Ld = dyn_cast<LoadSDNode>(Op0)) {
-      if (Ld->isSimple() && !Ld->isNonTemporal() &&
-          Ld->getExtensionType() == ISD::NON_EXTLOAD) {
-        SDVTList Tys = DAG.getVTList(VT, MVT::Other);
-        SDValue Ops[] = {Ld->getChain(), Ld->getBasePtr()};
-        SDValue BcastLd =
-            DAG.getMemIntrinsicNode(X86ISD::SUBV_BROADCAST_LOAD, DL, Tys, Ops,
-                                    Ld->getMemoryVT(), Ld->getMemOperand());
-        DAG.ReplaceAllUsesOfValueWith(
-            Op0,
-            extractSubVector(BcastLd, 0, DAG, DL, Op0.getValueSizeInBits()));
-        DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1), BcastLd.getValue(1));
-        return BcastLd;
-      }
-    }
-
     // concat_vectors(movddup(x),movddup(x)) -> broadcast(x)
     if (Op0.getOpcode() == X86ISD::MOVDDUP && VT == MVT::v4f64 &&
         (Subtarget.hasAVX2() ||