[clang] [clang] Make -fveclib={ArmPL, SLEEF} imply -fno-math-errno (PR #112580)

[David Truby via cfe-commits]

DavidTruby wrote:

> Have you checked the flang driver? Is it not applicable there since errno is not used in Flang?

We don't support the gfortran extension for checking errno in flang and I can't see another way of checking it portably, so I wonder if we should just have this flag on by default in flang in general? It shouldn't provide any observable change and might increase performance as far as I can tell.

We also don't actually check errno in any of the math calls in the Fortran runtime either so we might want it on when building there as well.

The change for clang looks good to me but don't want to "approve" as this probably needs someone with more specific knowledge of the clang side of things.

https://github.com/llvm/llvm-project/pull/112580