Reg: Restricting optimization and CR register usage

[Ian Lance Taylor]

Void_Star <praveen_athimon@rediffmail.com> writes:

> Also, I have come across this macro CONDITIONAL_REGISTER_USAGE which modify
> fixed_regs and call_used_regs to 1 for each of the registers in the classes
> which should not be used by GCC. 
> (http://gcc.gnu.org/onlinedocs/gccint/Register-Basics.html#Register-Basics
> ). But I do not have idea as how to and where to have this macro. Could any
> of you please help me out?

You are looking at the gcc internals manual.  That is a macro in the gcc
source code.  You can change it in your gcc sources, in this case by
changing the function rs6000_conditional_register_usage in
gcc/config/rs6000/rs6000.c.  Then you can rebuild gcc.

However, I would recommend using the -ffixed-REG options you listed.
That seems much simpler and will work with every version of gcc, not
just the ones you build yourself.

Ian