On Thu, Dec 18, 2014 at 10:58:02PM +0000, Matthew Fortune wrote: > Yes you are right I thought this particular case only had constraints > for the immediate and not the whole memory operand, I'm suffering from > too many tasks and too little time. Several of the memory constraints are > marked as internal and I'm not sure if that means they are unsafe to use > from inline asm or just not deemed important. > > The memory constraint that LL and SC need is 'ZC'. I don't believe this > is documented so you will have to trust that its meaning will not change > but I can give some assurance of that since I will review all MIPS GCC > changes. > > Obviously to use anything other than the 'm' constraint you are going > to need to know when any given constraint was added to GCC. > 'ZC' was only added to GCC in March 2013 r196828 which I believe it is a > GCC 4.9 feature so you will have to use it conditionally if you use it at > all. > > BTW thanks for the thread, it seems I missed updating 'ZC' for MIPSR6. > Bug fixed! How about the "o" constraint? The kernel uses it only in a few places and not currently with LL/SC though that might allow for some extra optimization(?). Is the a suitable "o"-like constraint for use with LL/SC on R6? Ralf
