[llvm] [InstCombine] Fold `fcmp (fmul X, C1), C2` to `fcmp X, C2/C1` (PR #205003)

[Matt Arsenault via llvm-commits]

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arsenm wrote:

Don't understand the denormal mode check. You are not obligated to do any flushing, this can always evaluate as IEEE 

https://github.com/llvm/llvm-project/pull/205003