andykaylor wrote:

> One final nit before you submit, though: please update the PR description and 
> the release notes to also mention that x86 no longer modifies 
> `-fdenormal-fp-math` based on `-ffast-math`.

The Clang User's Manual makes some contradictory statements about this. In one 
place it says, `-fno-fast-math` resets `-fdenormal-fp-math=<value>` to its 
target-dependent default, but just a few lines later it says "-fno-fast-math 
implies -fdenormal-fp-math=ieee" which isn't true for all targets. It says 
`-fno-unsafe-math-optimizations` implies '-fdenormal-fp-math=ieee` which, 
unfortunately, is currently be true.

The User's Manual also says that `-ffp-model=fast` sets `denormal_fp_math` to 
IEEE, which is currently true, but really shouldn't be.

I'm working on a PR to fix the fp-model handling, which I'll update after this 
PR lands. I can fix the other issues I've mentioned here in that patch. There 
are a few points that I am not quite clear on. I'm going to start a Discourse 
topic to summarize what we've agreed on here and discuss the things I'm not 
sure about.

https://github.com/llvm/llvm-project/pull/80475
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