[llvm] [AMDGPU] Improve MIR pattern for FMinFMaxLegacy combine. NFC. (PR #90968)

[Jay Foad via llvm-commits]

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@@ -15,8 +15,9 @@ def fmin_fmax_legacy_matchdata : GIDefMatchData<"FMinFMaxLegacyInfo">;
 let Predicates = [HasFminFmaxLegacy] in
 def fcmp_select_to_fmin_fmax_legacy : GICombineRule<
   (defs root:$select, fmin_fmax_legacy_matchdata:$matchinfo),
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jayfoad wrote:

Am I supposed to list `$fcmp` in the defs since I am passing it into my match function? Or doesn't that count as an "external" use of `$fcmp`?

https://github.com/llvm/llvm-project/pull/90968