[cfe-users] Is it possible to translate or forward flags from clang to llc?

[Massimiliano Culpo via cfe-users]

Hi,

I'm looking into what could be the best way to add compiler flags for Clang
to emit optimized code for a specific chip on a given architecture.

Looking at various sources I saw that:

   - llc -march=<architecture> -mcpu=help

returns the list of the supported cpus which is already helpful. The piece
of information I'm currently missing is how to translate llc's flags like:

   - `-march=x86-64 -mcpu=broadwell`
   - `-march=aarch64 -mattr=+v8.1a,+fp-armv8,+neon,+crc,+crypto`

etc. into something that is understood by clang.

In case the context for doing this is of interest, I'm a core developer of
a package manager focused on HPC (https://github.com/spack/spack) and we'll
use this information to automatically inject optimization flags when
installing application from sources based on the chip selected by the user.

Cheers,
Massimiliano Culpo
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