Re: RFC: [PATCH] MIPS: Implement built-in atomic memory operations.

[David Daney <ddaney at avtrex dot com>]

Maciej W. Rozycki wrote:
> > > For a Linux configuration with MIPS I this should also be true,
> > > the kernel emulates ll/sc in those cases.
> > >
> > >   
> > >       
> > In this case could you "lie" to the compiler by passing -mips2 on the command
> > line?  Otherwise we would have to either leave it as it is or add a new
> > command line parameter to explicitly enable ll/sc.
> >     
>
>  I would feel a bit uneasy about adding the implication of the 
> availability of ll/sc based on the target operating system.  Using a 
> switch like "-march=mips2" is unacceptable as it enables some other 
> instructions.  I would be in favour to an additional option along the 
> lines of -mbranch-likely.
>
>   
Something like -mllsc.  The default value could be set at configure time 
with --with-llsc=[true|false]. Perhaps mips*-*-linux* would imply 
--with-llsc=true unless overridden.  Done in a similar manner to the 
default -march and -msoft-float settings.

Perhaps Richard could opine on the matter.

David Daney