[PATCH] D91716: AMDGPU/GlobalISel: Calculate isKnownNeverNaN for fminnum and fmaxnum

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/CodeGen/GlobalISel/Utils.cpp:498-499
+    case TargetOpcode::G_FMAXNUM: {
+      const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
+      return TLI->isKnownNeverNaNForMI(Val, MRI, SNaN);
+    }
----------------
Petar.Avramovic wrote:
> Can this then be `return true`?
No, it depends on the inputs. You can refer to the existing SelectionDAG::isKnownNeverNaN:

```
    // Only one needs to be known not-nan, since it will be returned if the
    // other ends up being one.
    return isKnownNeverNaN(Op.getOperand(0), SNaN, Depth + 1) ||
           isKnownNeverNaN(Op.getOperand(1), SNaN, Depth + 1);

```


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91716/new/

https://reviews.llvm.org/D91716