[llvm] SelectionDAG: Support FMINIMUMNUM and FMINIMUM in combineMinNumMaxNumImpl (PR #137449)

[Matt Arsenault via llvm-commits]

================
@@ -11919,38 +11928,70 @@ static SDValue combineMinNumMaxNumImpl(const SDLoc &DL, EVT VT, SDValue LHS,
                                        const TargetLowering &TLI,
                                        SelectionDAG &DAG) {
   EVT TransformVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  unsigned IEEE2019NumOpcode = 0;
+  unsigned IEEE2019Opcode = 0;
+  unsigned IEEEOpcode = 0;
+  unsigned Opcode = 0;
   switch (CC) {
   case ISD::SETOLT:
   case ISD::SETOLE:
   case ISD::SETLT:
   case ISD::SETLE:
   case ISD::SETULT:
   case ISD::SETULE: {
-    // Since it's known never nan to get here already, either fminnum or
-    // fminnum_ieee are OK. Try the ieee version first, since it's fminnum is
-    // expanded in terms of it.
-    unsigned IEEEOpcode = (LHS == True) ? ISD::FMINNUM_IEEE : ISD::FMAXNUM_IEEE;
-    if (TLI.isOperationLegalOrCustom(IEEEOpcode, VT))
-      return DAG.getNode(IEEEOpcode, DL, VT, LHS, RHS);
-
-    unsigned Opcode = (LHS == True) ? ISD::FMINNUM : ISD::FMAXNUM;
-    if (TLI.isOperationLegalOrCustom(Opcode, TransformVT))
-      return DAG.getNode(Opcode, DL, VT, LHS, RHS);
-    return SDValue();
+    // Since it's known never nan to get here already, either fminimumnum,
+    // fminimum, fminnum, or fminnum_ieee are OK. Try Legal first and then
+    // Custom.
+    IEEE2019NumOpcode = LHS == True ? ISD::FMINIMUMNUM : ISD::FMAXIMUMNUM;
+    IEEE2019Opcode = LHS == True ? ISD::FMINIMUM : ISD::FMAXIMUM;
+    IEEEOpcode = LHS == True ? ISD::FMINNUM_IEEE : ISD::FMAXNUM_IEEE;
+    Opcode = LHS == True ? ISD::FMINNUM : ISD::FMAXNUM;
   }
+    [[fallthrough]];
   case ISD::SETOGT:
   case ISD::SETOGE:
   case ISD::SETGT:
   case ISD::SETGE:
   case ISD::SETUGT:
   case ISD::SETUGE: {
-    unsigned IEEEOpcode = (LHS == True) ? ISD::FMAXNUM_IEEE : ISD::FMINNUM_IEEE;
-    if (TLI.isOperationLegalOrCustom(IEEEOpcode, VT))
+    if (Opcode == 0) {
----------------
arsenm wrote:

```suggestion
    if (Opcode == ISD::DELETED_NODE) {
```

https://github.com/llvm/llvm-project/pull/137449