[cfe-dev] [ARM] Removing v7s/v7f/v7k and cortex-a9-mp

[Evan Cheng]

Can you clarify what you are proposing? Are you proposing that we eliminate the option such as -arch armv7s? If so, the answer is no. This would impact a lot of users negatively. 

If you are proposing changes to how the information is communicated between the frontend and backend, then the answer is maybe. You do need to provide a much more concrete proposal that will maintain the functionality. 

Evan

> On Nov 7, 2013, at 5:15 AM, Bradley Smith <bradley.smith at arm.com> wrote:
> 
> Hi,
> 
> I'd like to propose making a change in the ARM backend such that the MP
> extensions subtarget feature is enabled by default on all CPUs with this
> extension, however this has an impact on various other areas of Clang and
> LLVM.
> 
> Most notably, Clang has a CPU name, cortex-a9-mp, that should be gotten rid
> of as part of this change since it will be redundant in terms of subtarget
> features enabled, (it would be identical to cortex-a9). However currently,
> this CPU name maps to an architecture of armv7f. This looks to be a pseudo
> architecture that from what I can gather is only used for the CPUSubType
> field in the Mach-O header.
> 
> In order to avoid keeping this cortex-a9-mp CPU around (since it will just
> be a source of confusion), I would also like to propose removing these
> Mach-O specific architectures from Clang (7f, 7s, 7k) and instead pass this
> information through to LLVM in a different manner, perhaps by changing the
> CPUSubType logic in the ARM backend to be based upon CPU rather than these
> pseudo architectures, or by passing it by command line? (I'm guessing care
> will need to be taken to avoid letting CPUs that don't map to a valid
> CPUSubType get through?).
> 
> Both of these changes should make the Clang driver a bit more sane in these
> areas, so I think these are both generally good changes to do. Does anybody
> have any comments/objections to this? Specifically, am I right in thinking
> that the Mach-O header is the only place these pseudo architectures are
> being used? What would be the right approach for getting the CPUSubType
> information through to LLVM?
> 
> Regards,
> Bradley Smith
> 
> 
> 
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