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

[Thorsten Schütt 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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tschuett wrote:

No. I prefer to only list the `$root`. defs is probably definitions and not def in SSA.

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