http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53726
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
CC| |hubicka at gcc dot gnu.org
--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-20
11:48:13 UTC ---
Ok. A rep movsb; is as slow as a memcpy call (-mstringop-strategy=rep_byte
-minline-all-stringops). -minline-all-stringops itself is nearly as fast
as -fno-tree-loop-distribute-patterns.
To answer my own question, BC is between zero and 7.
But I really wonder why the rep movsb is slower than the explicit byte-copy
loop ...
We do seem to seriously hose the CFG though - with PGO we get a nice
loop nest CFG and the speed of before the patch - even when it uses
a memcpy call.
