Does IRA support spilling to registers instead of stack?

[Vladimir Makarov]

On 07/18/2011 05:20 PM, dpadgett_mail-000@yahoo.com wrote:
> Hello,
>
> Does gcc IRA provide a mechanism to support spilling to registers instead of the stack?  For the particular target I'm looking at, there are some non-general-purpose registers that can be copied to and from more quickly than the stack, so would be preferable to use as a form of shareable spill slot in some cases.  One limitation, which is perhaps a significant one, is that these registers are not callee save, so one would only want to save to and restore from them when there is no intervening function call. If there is no current support for such a mechanism, any opinions on the value and practicality of adding one would be much appreciated.
>
> Thanks, Don
It might work for new IRA without cover classes.

Pseudos will have classes containing usual registers and these special 
registers because they are really less costly than memory.  If a pseudo 
crosses a call, the special registers could be more costly than memory.

All you need is to define the right costs for register and memory move 
cost hooks to achieve better costs for regular registers, worse costs 
for the special registers, and the worst cost for memory.  If the pseudo 
intersects the call, the worst cost should be for the special 
registers.  It can be achieved by right definition of move cost between 
special registers and memory.