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

[Craig Topper via cfe-commits]

================
@@ -8262,6 +8262,64 @@ 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 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 {
+    SDValue Compare =
+        DAG.getSetCC(DL, CCVT, LHS, RHS, IsMax ? ISD::SETGT : ISD::SETLT);
----------------
topperc wrote:

SETGT/SETLT leave it up to the target whether it returns true or false for NaN. Is that intentional? If so it's probably worth a comment.

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