Re: Proposed doc update for Explicit Reg Vars 2/3

[Segher Boessenkool <segher at kernel dot crashing dot org>]

On Tue, Oct 20, 2015 at 09:24:48PM -0700, David Wohlferd wrote:
> >>+Registers can be a limited resource on some systems and allowing the
> >They are a limited resource on almost all systems.  "Scarce resource"?
> 
> "Scarce" it is.  I've left the rest alone for the moment, but how would 
> you feel about:
> 
> "Registers are a scarce resource on most systems and allowing the"

That sounds fine.

> >>+All global register variable declarations must precede all function
> >>+definitions.  If such a declaration appears after function definitions,
> >>+the declaration would be too late to prevent the register from being used
> >>+for other purposes in the preceding functions.
> >This isn't true anymore, not even with -fno-toplevel-reorder or -O0.
> 
> I'm going to interpret this as a recommendation to remove this text, 
> rather than just an FYI.  Done.

Perfect.

> >>+When selecting a register, choose one that is normally saved and
> >>+restored by function calls on your machine.  This ensures that code
> >>+which is unaware of this reservation (such as library routines) will
> >>+restore it before returning.
> >The compiler also warns, possibly for the unlikely case that the user has
> >not read the documentation.
> 
> I'm going to interpret this comment as just an FYI, and NOT something 
> that should be added to the docs.

That is fine of course.

Cheers,


Segher