[llvm] [AMDGPU] Adjust amdgpu fmax/fmin legalization for DAG (PR #203150)

[Matt Arsenault via llvm-commits]

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@@ -539,15 +539,35 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
     setOperationAction({ISD::SADDSAT, ISD::SSUBSAT}, {MVT::i16, MVT::i32},
                        Legal);
 
-  setOperationAction(
-      {ISD::FMINNUM, ISD::FMAXNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
-      {MVT::f32, MVT::f64}, Custom);
-
-  // These are really only legal for ieee_mode functions. We should be avoiding
-  // them for functions that don't have ieee_mode enabled, so just say they are
-  // legal.
-  setOperationAction({ISD::FMINNUM_IEEE, ISD::FMAXNUM_IEEE},
-                     {MVT::f32, MVT::f64}, Legal);
+  // Do not have s_{min|max}_*f64 instruction f64 will only be lowered to
+  // v_{min|max}_*f64
+  if (Subtarget->hasIEEEMinimumMaximumInsts()) {
+    setOperationAction(
+        {ISD::FMINNUM, ISD::FMAXNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
+        MVT::f64, Legal);
+  } else {
+    setOperationAction(
+        {ISD::FMINNUM, ISD::FMAXNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM},
+        MVT::f64, Custom);
+    // These are really only legal for ieee_mode functions. We should be
+    // avoiding them for functions that don't have ieee_mode enabled, so just
+    // say they are legal.
+    setOperationAction({ISD::FMINNUM_IEEE, ISD::FMAXNUM_IEEE}, MVT::f64, Legal);
+  }
+
+  // If has v_{min|max}_num_f32 but no s_{min|max}_num_f32, leave it for custom
+  // function
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arsenm wrote:

The scalar form shouldn't matter here? Both were introduced at the same time in gfx12 too. I'd just remove the hasSALU* check 

https://github.com/llvm/llvm-project/pull/203150