[llvm] [NFC] Add useFPRegsForHalfType(). (PR #74147)

[Harald van Dijk via llvm-commits]

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@@ -505,12 +505,18 @@ class TargetLoweringBase {
     return TypePromoteInteger;
   }
 
-  // Return true if the half type should be passed around as i16, but promoted
-  // to float around arithmetic. The default behavior is to pass around as
-  // float and convert around loads/stores/bitcasts and other places where
-  // the size matters.
+  // Return true if the half type should be promoted using soft promotion rules
+  // where each operation is promoted to f32 individually, then converted to
+  // fp16. The default behavior is to promote links of operations, keeping
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hvdijk wrote:

Yes, thank you. I struggled to find the right wording, managed to remember to update it in the commit message and MR description, but forgot to also update the comment. Fixed.

https://github.com/llvm/llvm-project/pull/74147