http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56083
--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2013-01-23 16:23:47 UTC --- (In reply to comment #2) > Uros, I completely agree, but note that the PR also mentions this line: > > xorps %xmm0, %xmm0 > > which appears rather useless since the low and high parts are overwritten on > the next 2 lines. Is this done on purpose to kill dependencies or something? > Or > is it a missed optimization? (simplify-rtx (or another place) is indeed > missing > a few things in that area) IIRC, this insn is emitted to break dependency chain for %xmm0 register. Processor is not _that_ smart ;)
