[cfe-dev] [LLVMdev] AArch64 Clang CLI interface proposal

[Eric Christopher]

We typically add options in clang only if there is a user for them.
On Jan 8, 2014 4:32 AM, "Bernard Ogden" <Bernard.Ogden at arm.com> wrote:

>  I'm just stating that _if_ GCC compatibility is desired then we have to
> have -mcpu.
>
>
>
> I don't think there's software that *needs* the compatibility, but it is
> easier for GCC projects to switch to clang if that compatibility is there -
> which I think is why we go for GCC compatibility in the first place?
>
>
>
> (I raised http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59718 on the GCC
> docs.)
>
>   *From:* Eric Christopher [mailto:echristo at gmail.com]
> *Sent:* 08 January 2014 12:23
> *To:* Bernard Ogden
> *Cc:* Renato Golin; LLVM Developers Mailing List; Clang Dev; Amara Emerson
> *Subject:* RE: [cfe-dev] [LLVMdev] AArch64 Clang CLI interface proposal
>
>
>
> I knew I'd regret leaving that option in for the MIPS port back in 99.
> Basically this is the only acceptable way for mcpu to exist, but should
> never have been added to the GCC aarch64 port at all since there's no
> compatibility with existing build systems to worry about.
>
> I would still like you to show this mythical piece of software that needs
> this compatibility.
>
> -eric
>
> On Jan 8, 2014 3:06 AM, "Bernie Ogden" <bogden at arm.com> wrote:
>
> I think there's an error in the example here.
> http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/AArch64-Options.html still
> documents -mcpu, and that march does not take CPUs as arguments. A local
> GCC developer tells me that the documentation is wrong in that -mcpu is
> actually a shorthand for specifying both -mtune and -march, but that the
> option is certainly there.
>
>
>
> If we want GCC comptability then that's what we have to do, unless someone
> knows that GCC ARM/AArch64 is actually going to move away from this.
>
>
>
> Do we want GCC compatibility?
>
>
>
> Regards,
>
>
>
> Bernie
>
>
>
>
>
> *From:* cfe-dev-bounces at cs.uiuc.edu [mailto:cfe-dev-bounces at cs.uiuc.edu] *On
> Behalf Of *Eric Christopher
> *Sent:* 07 January 2014 21:37
> *To:* Renato Golin; Amara Emerson; Clang Dev; LLVM Dev
> *Subject:* Re: [cfe-dev] [LLVMdev] AArch64 Clang CLI interface proposal
>
>
>
> Parsing the arch string is a bit icky, but I don't really have too much of
> a problem with it - and it's better than -mcpu so...
>
>
>
> -eric
>
>
>
> On Tue Jan 07 2014 at 9:23:43 AM, Renato Golin <renato.golin at linaro.org>
> wrote:
>
>   On 7 January 2014 17:05, Amara Emerson <amara.emerson at arm.com> wrote:
>
> We plan on implementing this interface for AArch64 Clang in future, and
> completely dropping the current support for -mfpu. This means that -march
> will become the preferred way to specify the target CPU/architecture.
>
>
>
> Hi Amara,
>
>
>
> This is something we were converging on the ARM32 world, too, and I
> believe other targets would probably do the same, if not before us.
> Hopefully, that'd also help clean up the driver's code in the process.
>
>
>
> cheers,
>
> --renato
>
>
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