[PATCH] [AArch64] Implement Clang CLI interface proposal about "-march".

[Kristof Beyls]

Thanks for the feedback, Eric.

I've thought further about the potential deprecation of -mcpu.
TBH, I haven't seen any good reason for deprecating -mcpu.  I've
looked through the discussion threads on this topic on the LLVM
mailing lists and tried to find discussions on the gcc side about
deprecating -mcpu. I haven't found any strong arguments to
deprecate -mcpu for the AArch64 architecture.

Therefore, I don't see a good reason for implementing 
-march/-mcpu/-mtune option behaviour for AArch64 any other way
than gcc does it.

Thanks,

Kristof

> -----Original Message-----
> From: Eric Christopher [mailto:echristo at gmail.com]
> Sent: 09 July 2014 19:49
> To: Kristof Beyls
> Cc: Kevin Qin; Clang Commits; kanheim at a-bix.com; LLVM Commits;
> reviews+D4346+public+5fab7236f933ff44 at reviews.llvm.org
> Subject: Re: [PATCH] [AArch64] Implement Clang CLI interface proposal
> about "-march".
> 
> > * On deprecating -mcpu: I think that should be left to a follow-on
> >   patch and probably needs some further discussing, as I'm not
> >   fully convinced it's the right thing to do. If we did deprecate
> >   -mcpu, I do think that we would have to start accepting cpu
> >   names to the -march flag, as a shorthand for "the architecture
> >   variant as implemented by that CPU". For example, -march cortex-a57
> >   would be equivalent to specifying -march armv8-a+fp+simd+crypto+crc.
> >   We would also lose command line compatibility with gcc, which
> >   would make it harder for people using gcc to start trying out clang.
> 
> Let's just have -march=cyclone/cortex-a57 work right from the start and
> we won't have to worry about it.
> 
> Thanks.
> 
> -eric