movmem pattern and missed alignment

[Eric Botcazou]

> It's not quite obvious what SSE has to do with this - any hint please?

SSE introduced alignment constraints into the non-strict-alignment target x86 
so people didn't really want to play by the rules of strict-alignment targets.

> (according to my quick check this changed between gcc-4.5 and gcc-4.6)

Possibly indeed, I remembered GCC 4.5 as being the turning point.

-- 
Eric Botcazou