[llvm-branch-commits] [SPARC] Use op-then-halve instructions when we have VIS3 (PR #135718)

[Matt Arsenault via llvm-branch-commits]

================
@@ -3613,13 +3613,15 @@ bool SparcTargetLowering::isFNegFree(EVT VT) const {
 
 bool SparcTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT,
                                        bool ForCodeSize) const {
+  bool CanLower = false;
   if (VT != MVT::f32 && VT != MVT::f64)
     return false;
-  if (Imm.isZero())
-    return Subtarget->isVIS();
-  if (Imm.isExactlyValue(+0.5) || Imm.isExactlyValue(-0.5))
-    return Subtarget->isVIS3();
-  return false;
+  if (Subtarget->isVIS())
+    CanLower = CanLower || Imm.isZero();
+  if (Subtarget->isVIS3())
+    CanLower =
+        CanLower || (Imm.isExactlyValue(+0.5) || Imm.isExactlyValue(-0.5));
+  return CanLower;
----------------
arsenm wrote:

```suggestion
  if (Subtarget->isVIS3())
    return Imm.isExactlyValue(+0.5) || Imm.isExactlyValue(-0.5);

  return false;
```

Could also use getExactLog2Abs == -1?

https://github.com/llvm/llvm-project/pull/135718