[llvm] [SDAG][X86] Form pseudo fmin/fmax from select_cc (PR #208717)

[Simon Pilgrim via llvm-commits]

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@@ -13194,23 +13188,46 @@ static SDValue combineSelectToPseudoMinMax(SelectionDAG &DAG, SDNode *N) {
   }
 
   if (!Opcode)
-    return SDValue();
+    return Invalid;
 
   if (IsStrict)
     Opcode = Opcode == ISD::PSEUDO_FMIN ? ISD::STRICT_PSEUDO_FMIN
                                         : ISD::STRICT_PSEUDO_FMAX;
   if (!TLI.isOperationLegalOrCustom(Opcode, VT))
+    return Invalid;
+
+  return {Opcode, LHS, RHS};
+}
+
+static SDValue combineSelectToPseudoMinMax(SelectionDAG &DAG, SDNode *N) {
+  SDLoc DL(N);
+  SDValue Cond = N->getOperand(0);
+  SDValue LHS = N->getOperand(1);
+  SDValue RHS = N->getOperand(2);
+  EVT VT = LHS.getValueType();
+  if ((Cond.getOpcode() != ISD::SETCC &&
+       Cond.getOpcode() != ISD::STRICT_FSETCCS))
+    return SDValue();
+
+  bool IsStrict = Cond->isStrictFPOpcode();
+  ISD::CondCode CC =
+      cast<CondCodeSDNode>(Cond.getOperand(IsStrict ? 3 : 2))->get();
+  SDValue Op0 = Cond.getOperand(IsStrict ? 1 : 0);
+  SDValue Op1 = Cond.getOperand(IsStrict ? 2 : 1);
+  auto [Opcode, NewLHS, NewRHS] = combineSelectCCToPseudoMinMax(
+      DAG, DL, CC, Op0, Op1, LHS, RHS, N->getFlags(), IsStrict);
+  if (!Opcode)
     return SDValue();
 
   // Propagate fast-math-flags.
   SelectionDAG::FlagInserter FlagsInserter(DAG, N->getFlags());
   if (IsStrict) {
-    SDValue Ret = DAG.getNode(Opcode, DL, {N->getValueType(0), MVT::Other},
-                              {Cond.getOperand(0), LHS, RHS});
+    SDValue Ret = DAG.getNode(Opcode, DL, {VT, MVT::Other},
+                              {Cond.getOperand(0), NewLHS, NewRHS});
     DAG.ReplaceAllUsesOfValueWith(Cond.getValue(1), Ret.getValue(1));
     return Ret;
   }
-  return DAG.getNode(Opcode, DL, N->getValueType(0), LHS, RHS);
+  return DAG.getNode(Opcode, DL, VT, NewLHS, NewRHS);
----------------
RKSimon wrote:

I get splitting the SDNode into component operands - but why do we need to return the opcode/ops and then create the nodes in the caller? 

https://github.com/llvm/llvm-project/pull/208717