__AVX2__ not set by `zig cc` when using `-x assembler-with-cpp`

[hanno-becker]

Zig Version

0.13.0

Steps to Reproduce and Observed Behavior

$ nix --version
nix (Nix) 2.24.9
$ nix-shell -p zig
[nix-shell:~/]$ zig cc -mavx2 -dM -E  - </dev/null | grep AVX
#define __AVX2__ 1
#define __AVX__ 1

[nix-shell:~/]$ zig cc -mavx2 -dM -E -x assembler-with-cpp - </dev/null | grep AVX

[nix-shell:~/]$

Expected Behavior

-mavx2 should lead to __AVX2__ being defined regardless of whether .c or .S files are processed. Instead, -x assembler-with-cpp leads to __AVX2__ not being defined.

[hanno-becker]

@alexrp Thank you for flagging the duplicate 👍 Could you clarify, ideally for the case at hand, whether there is a workaround?

[alexrp]

I'm not personally aware of a workaround for this at the moment.

I might try to prod upstream at some point to see if they'll reconsider llvm/llvm-project#100714.

[hanno-becker]

@alexrp Ack, thanks for the fast reply!