[i386] scalar ops that preserve the high part of a vector

[Richard Henderson]

On 2012-12-07 09:00, Marc Glisse wrote:
> On Fri, 7 Dec 2012, Richard Henderson wrote:
> 
>> On 2012-12-07 02:49, Marc Glisse wrote:
>>> For 2-element vectors, vec_concat does seem more natural than
>>> vec_merge. If we chose vec_merge as the canonical representation, we
>>> should chose it for setting an element in a vector
>>> (ix86_expand_vector_set) everywhere, not just those scalarish
>>> operations.
>>
>> I'd hate to enshrine vec_merge over vec_concat for the benefit of x86,
>> and to the detriment of e.g. mips.  There are plenty of embedded simd
>> implementations that are V2xx only.
>>
>> If we simply pull the various x86 patterns into one common form, set
>> and extract included, does that buy us most of what we'd get for
>> playing games in combine?
> 
> I'm sorry, could you be more precise? I don't see clearly what you are suggesting.

Don't change combine?

Have I lost the plot somewhere here?


r~