[Bug middle-end/52835] [4.7/4.8 Regression] -O3 wrongly optimizes loop __builtin_memcpy away

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52835

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2012-04-02 
16:18:47 UTC ---
r183622 is OK
r183649 miscompiles the code.