[llvm] r185527 - ARM: relax the atomic release barrier to "dmb ishst" on Swift

[Jeffrey Yasskin]

On Wed, Jul 3, 2013 at 10:34 AM, Tim Northover <t.p.northover at gmail.com> wrote:
>> In general, when adding these optimizations, can you try to link to
>> the documentation that justifies the change?
>
> Tricky, particularly in cases like this. Virtually no-one makes
> microarchitectural documentation public these days because of the
> patent trolls.

Grr. This is API documentation for their version of ARM; it doesn't
need to specify how they accomplish something in order to say what
guarantees they provide to users of particular instructions. Not your
fault, of course.

> For things that are truly architectural, at least on ARM, the standard
> reference is the "ARM Architecture Reference Manual", which has
> standing links (alongside ABIs etc) in docs/CompilerWriterInfo.rst.
>
> I suppose a mention of the section number in the commit message
> wouldn't be out of place though in the more esoteric cases. I'll try
> to remember in future.
>
> Tim.