On 07/07/2014 09:35 AM, Uros Bizjak wrote:
> On Mon, Jul 7, 2014 at 5:01 PM, Richard Henderson <r...@redhat.com> wrote:
>
>> Early alpha can't store sub-4-byte quantities. Altivec can't store anything
>> but 16 byte quantities. In order to perform smaller stores, we have to do a
>> read-modify-write sequence on a larger aligned chunk of memory. Two such RMW
>> sequences must conflict, lest we interleave and thus bork the operation.
>>
>> I don't recall how much we ever did for this, exactly, but it's certainly
>> possible to know that some memory operations cannot conflict with these RMW
>> sequence. E.g. through size + alignment of the other memory operation. E.g.
>> on Alpha, a byte RMW store can't conflict with a normal DImode memory access.
>>
>>> Btw, if the mem is MEM_READONLY_P how can it be part of
>>> a {un}aligned_store sequence?
>>
>> Er... that's an excellent question. Uros?
>
> This flag is copied from the original memory operand by
> alpha_set_memflags to all memory operands in the expanded sequence.
Misses the point. Store on a MEM_READONLY_P?
I suppose I should take a closer look today...
r~
