[llvm-commits] two-byte return optimization for AMD

[Chris Lattner]

On Dec 7, 2008, at 11:39 PM, Evan Cheng wrote:

>
> On Dec 7, 2008, at 11:10 PM, Chris Lattner wrote:
>
>>
>> On Dec 7, 2008, at 11:04 PM, Evan Cheng wrote:
>>
>>> I am not crazy about adding a subtarget feature for a micro-
>>> optimization. If you want to enable a family of optimizations for  
>>> AMD
>>> chips, please just add something like a FeatureAMD feature.
>>
>> Why not?  What if some AMD chips have this "feature/problem" and
>> others don't?
>>
>
> I don't know. The problem with using SubtargetFeature for these is you
> can easily have an explosion of "features". But these are not
> features, they are micro-optimizations, errata workarounds. I'd rather
> break AMD into a several AMD families and teach x86 which families
> suffer from this.

Okay, it's your call.  Please make this its own method on X86Subtarget  
at least (which can grovel around with the selected cpu), even if  
there is no feature in the .td file.  The problem with not making this  
a feature is that you can't turn it n with -mattr.

-Chris