http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47167
--- Comment #6 from Uros Bizjak <ubizjak at gmail dot com> 2011-01-06 07:38:11 UTC --- (In reply to comment #5) > Some loop performance is very sensitive to code sizes. This change > > - mulpd %xmm10, %xmm2 > + mulpd %xmm0, %xmm2 > > will impact loop size due to exta REX prefix. Adding nop (or several of them, FWIW) around changed mulpd insn does not affect the performance, so IMO it is not the loop layout that matters in this case.
