[clang] [clang-tools-extra] [compiler-rt] [flang] [llvm] [Legalizer] Expand fmaximum and fminimum (PR #67301)

[Matt Arsenault via cfe-commits]

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@@ -8201,6 +8201,66 @@ SDValue TargetLowering::expandFMINNUM_FMAXNUM(SDNode *Node,
   return SDValue();
 }
 
+SDValue TargetLowering::expandFMINIMUM_FMAXIMUM(SDNode *N,
+                                                SelectionDAG &DAG) const {
+  SDLoc DL(N);
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+  unsigned Opc = N->getOpcode();
+  EVT VT = N->getValueType(0);
+  EVT CCVT = getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), VT);
+  bool NoNaN = (N->getFlags().hasNoNaNs() ||
+                (DAG.isKnownNeverNaN(LHS) && DAG.isKnownNeverNaN(RHS)));
+  bool NoZeroSign =
+      (N->getFlags().hasNoSignedZeros() || DAG.isKnownNeverZeroFloat(LHS) ||
+       DAG.isKnownNeverZeroFloat(RHS));
+  bool IsMax = Opc == ISD::FMAXIMUM;
+
+  if (VT.isVector() &&
+      isOperationLegalOrCustomOrPromote(Opc, VT.getScalarType()))
+    return SDValue();
+
+  // First, implement comparison not propagating NaN. If no native fmin or fmax
+  // available, use plain select with setcc instead.
+  SDValue MinMax;
+  if (isOperationLegalOrCustom(IsMax ? ISD::FMAXNUM_IEEE : ISD::FMINNUM_IEEE,
+                               VT))
+    MinMax = DAG.getNode(IsMax ? ISD::FMAXNUM_IEEE : ISD::FMINNUM_IEEE, DL, VT,
+                         LHS, RHS);
+  else if (isOperationLegalOrCustom(IsMax ? ISD::FMAXNUM : ISD::FMINNUM, VT))
+    MinMax = DAG.getNode(IsMax ? ISD::FMAXNUM : ISD::FMINNUM, DL, VT, LHS, RHS);
+  else
+    MinMax = DAG.getSelect(
+        DL, VT,
+        DAG.getSetCC(DL, CCVT, LHS, RHS, IsMax ? ISD::SETGT : ISD::SETLT), LHS,
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arsenm wrote:

Intermediate variable wouldn't hurt. Alternatively could use getSelectCC

https://github.com/llvm/llvm-project/pull/67301