r193740 - [AArch64] Add some CPU targets for "generic", A-53 and A-57.

Nigel Stephens Nigel.Stephens at arm.com
Mon Nov 11 12:49:29 PST 2013



> On 11 Nov 2013, at 07:24 pm, "Eric Christopher" <echristo at gmail.com> wrote:
>
> On Fri, Nov 8, 2013 at 9:02 AM, Tim Northover <t.p.northover at gmail.com> wrote:
>>> To me it would be odd if the AArch64 CLI behaved differently to AArch32,
>>> except where absolutely necessary.
>>
>> The general GCC interface has been encouraging -march/-mtune for years
>> now. I've no idea what reasons 32-bit ARM chose to go against that,
>> but I'd want to make sure they were valid for AArch64 before
>> perpetuating it.
>>
>> Inertia doesn't seem like a great reason except for ARM-only projects,
>> which are fairly rare.
>
> I agree with all of this.

Likewise.

The march/mtune mechanism seems to be the correct model, so long as it's clear that march specifies the base architecture name (I.e. what instructions/features are available to the compiler), and mtune a specific CPU name (I.e. how do those instructions behave on a specific microarchitecture). Confusion can reign if these get reversed!

Nigel

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