-mtune not supported to the assembler

[nlewycky]

Bugzilla Link	10079
Version	unspecified
OS	Linux
CC	@asl

Extended Description

$ clang -c -Wa,-mtune=i686 conftest.c
clang: error: unsupported argument '-mtune=i686' to option '-Wa,'

To my surprise, GNU as actually has this flag. I'm not sure if there's anything to wire it up to in MC (what does it actually do in GNU as?), but it'd be useful if we didn't error on it.

[llvmbot]

I think in gnu as it select how to produce large nops sequences. There is one algorithm for old (<= p4) cpus and one for newer cpus.

[asl]

Also, probably it's just another way to select target CPU/arch on, say, ARM.

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: None (nlewycky)

| | | | --- | --- | | Bugzilla Link | [10079](https://llvm.org/bz10079) | | Version | unspecified | | OS | Linux | | CC | @asl |

Extended Description

$ clang -c -Wa,-mtune=i686 conftest.c
clang: error: unsupported argument '-mtune=i686' to option '-Wa,'

To my surprise, GNU as actually has this flag. I'm not sure if there's anything to wire it up to in MC (what does it actually do in GNU as?), but it'd be useful if we didn't error on it.

[MaskRay]

In GNU assembler, -mtune= is implemented for mips, ia64, visium, and x86.
-mtune= is implemented for mips, ia64 (Itanium), visium, and x86.
The Itanium port uses -mtune= just to decide the desired NOP sequence. The x86 port -mtune= copies this design in 2006.

I am not sure this is still relevant today.

Unless more significant uses arise, I don't think -mtune= justifies an integrated assembler option.

(Clang does not support -Wa,-mtune=. I dropped a glibc use in i386: Remove -Wa,-mtune=i686.)