[PATCH] D11026: [ARM] Define subtarget feature "dont-use-movt" to disallow emitting movt/movw pairs

[Duncan P. N. Exon Smith]

> On 2015-Jul-08, at 16:16, Akira Hatanaka <ahatanak at gmail.com> wrote:
> 
> 
>> On 2015-Jul-08, at 13:52, Eric Christopher <echristo at gmail.com> wrote:
>> 
>> Let's have the feature be a positive feature that just happens to be on by default in a lot of places. +/-dont-use-movt seems weird.
>> 
> Do you mean I should replace ARMSubtarget::DontUseMovt with ARMSubtarget::UseMovt which is true by default? That should work.
> 
> Or do you mean we should use FeatureUseMovt : SubtargetFeature<"use-movt"> instead of FeatureDontUseMovt<"dont-use-movt">? If I understand correctly how subtarget features work, I think that would require clang (and other front-ends) to add feature "+use-movt" whenever we want to allow emitting movt/movw pairs as opposed to adding "+dont-use-movt" only when we want to disallow doing so. Assuming you would want to allow movt/movw pairs in the common case, wouldn't it be better to use a negative feature?

Maybe there's another negative name that isn't as strange.  Something
like "avoid-movt" or "no-movt"?