On Sun, Jun 24, 2012 at 09:01:34PM -0400, Joshua Kinard wrote: > I've maintained this patch, originally from Thiemo Seufer in 2004, for a > really long time, but I think it's time for it to get a look at for possible > inclusion. I have had no problems with it across various SGI systems over > the years. > > To quote the post here: > http://www.linux-mips.org/archives/linux-mips/2004-12/msg00000.html > > "the atomic functions use so far memory references for the inline > assembler to access the semaphore. This can lead to additional > instructions in the ll/sc loop, because newer compilers don't > expand the memory reference any more but leave it to the assembler. > > The appended patch uses registers instead, and makes the ll/sc > arguments more explicit. In some cases it will lead also to better > register scheduling because the register isn't bound to an output > any more." I have faint memories of having tried this myself and very ancient compilers didn't like the + constraint in inline assembler; somewhat less ancient compilers did generate slightly bigger code. With gcc 4.7 I am getting exactly the same codesize as without your patch applied. The patch shouldn't do anything to robustness but sureles makes the inline assembler a bit more readable so I'm queueing this for the next release. Thanks, Ralf
