Different register sets for local and global register allocation?

[Jim Wilson]

Jan Hoogerbrugge wrote:
> Is it possible to specify that part of the registers are available
> for local register allocation only and not for global register
> allocation?

No, but it might be possible to add.

The global register allocation pass in in global.c.  The entry point is 
global_alloc.  Near the top, there is a variable no_global_alloc_regs 
that gets initialized to regs that are unsafe to use across basic 
blocks.  Currently this only gets a few obvious things added to it, such 
as eliminable registers.  You could perhaps add a new macro, in the 
style of CALL_CLOBBERED_REGS, that specifies target dependent registers 
to add here.

You also need to make sure that reload doesn't try to use one of these 
registers across a basic block.

You will also have to check the new register allocator, in the ra-*.c 
files, and make this work there too.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com