On April 20, 2016 2:36:37 PM PDT, Borislav Petkov <b...@alien8.de> wrote: >On Wed, Apr 20, 2016 at 02:06:33PM -0700, H. Peter Anvin wrote: >> Setting ret to sem doesn't make any sense. Just use "=a" and "a". > >Yeah, that's what Michal's patch ontop does. > >And to answer my own question: we need the "a" (sem) input for the fast >path. > >I guess we can still move "1" (RWSEM_ACTIVE_WRITE_BIAS) before the >asm(): > > long tmp = RWSEM_ACTIVE_WRITE_BIAS; > >One thing I'm still not clear on is why we need the output tmp operand: >"=d" (tmp) ?
Since it is a fixed register we could just mark edx clobbered, but with more flexible register constraints it can permit gcc to allocate a temp resister for us. -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
