Re: [PATCH 0/5] Convert Sparc to atomic optabs

[Eric Botcazou <ebotcazou at libertysurf dot fr>]

> The first four patches simply do the conversion, a piece at a time,
> assuming the RMO for all cpus.

The new form of the membar_v8 insn looks a bit strange since operand 1 is 
disregarded.  If this is as intended, a comment would be in order.

> The fifth patch adds the ability to explicitly set the memory model
> for the program, and to adjust the barriers emitted based on that
> memory model.  If we agree on the spelling of that option (3 m's in
> a row seems fairly harsh) I'll write some documentation for it.

"memory model" is used consistently in the manual so, if the triple m is deemed 
too disturbing, -mmemory-model would be a little better.  In any case, I don't 
expect it to be used at all in practice.  And memory_order should be renamed 
into sparc_memory_model (or sparc_memmodel?) and the enum constants prefixed 
with MM (which is the name of the PSTATE register holding the value).

> An unwritten sixth patch would allow the default memory model to be
> set by the operating system, as Dave tells me that Linux always uses
> TSO.  And I guess when generating code specifically for Ultra-III,
> which doesn't implement the more relaxed models.

We should probably default to TSO for V8/V9 at this point.


This builds fine on Solaris, 32-bit and 64-bit, but I guess I'm seeing the ICE 
Dave reported.  Do you have a patchlet for it?

-- 
Eric Botcazou