[PATCH] Remove copies of MCSubtargetInfo from MCRelaxableFragment

[Duncan P. N. Exon Smith]

r241957
> On 2015-Jul-10, at 06:37, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
> 
> patch 3 LGTM.
> 
> On 10 July 2015 at 09:29, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>> Patch 2 LGTM.
>> 
>> On 10 July 2015 at 09:27, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>>> Patch 1 LGTM.
>>> 
>>> 
>>> On 8 July 2015 at 20:30, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
>>>> Last I checked my `-g -flto` workload, `MCRelaxableFragment` was taking
>>>> up 4.7% of the heap during LTO.  Since these aren't debug info related,
>>>> the relative cost is even higher without `-g` (I figure 10% or so?).
>>>> The struct layout contained a shock: over half of
>>>> `sizeof(MCRelaxableFragment)` comes from a local copy (!?) of
>>>> `MCSubtargetInfo`.
>>>> 
>>>> It was more roundabout than I expected to fix, but this patch series
>>>> does it.  0001 removes the copy of `MCSchedModel` from
>>>> `MCSubtargetInfo`, 0002-0004 change the `MCSubtargetInfo` API to prove
>>>> that only the feature bits get mutated, and 0005 moves the copies of
>>>> `MCSubtargetInfo` to a cache in `MCContext`.
>>>> 
>>>> I'd love a pre-commit sanity check from someone for two of these:
>>>>  - 0001 (the object for `MCSchedModel::GetDefaultMCSubtarget()` doesn't
>>>>    need to be defined in the header for some reason, does it?) and
>>>>  - 0003 (I'm touching *all* the targets...)
>>>> 
>>>> and I've provided the rest of the series (and a combined all.patch) for
>>>> context.
>>>> 
>>>>