More methods of reducing the register pressure

[Jeff Law]

On 04/19/2015 09:28 AM, Ajit Kumar Agarwal wrote:
> Hello All:
>
> To reduce the register pressure, I am proposing the following methods of reducing the registers.
>
> 1. Assigning same registers or sharing same register for the logical registers having the same value.
> To determine the logical registers having the same value is the real challenge. Is there is any way in
> GCC to determine the logical registers having the same value?
I believe Vlad looked at this 10+ years ago and it was of marginal/no 
real benefit.

>
> 2. For the architecture with the self-modifying instructions the DEF-USE will not overlap and can
> Do the better register allocator and thus reclaiming the registers when it's no longer used.
> Such self-modifying instructions can assign the same registers.
>
> For example:
>
> OP R1   -------------Definition.
> ...                                      .
> ...                                      No used.
> OP R1,R1 ----------------self-modifying.
> .....                                           .
> ......                                         Not Used
> OP R1, R1 ------------  Self-modifying.
I would think this would be handled by the normal life & conflict 
analysis which works on pseudos.

jeff