PING [Patch][Middle-end]Add -fzero-call-used-regs=[skip|used-gpr|all-gpr|used|all]

[Segher Boessenkool]

On Fri, Sep 11, 2020 at 06:32:56PM +0100, Richard Sandiford wrote:
> Unlike Segher, I think this can/should be done in target-independent
> code as far as possible (like the patch seemed to do).

My problem with that is that it is both incorrect *and* inefficient.  It
writes registers it should not touch; and some of those will be written
with other values later again anyway; and if the goal is to clear as
many parameter passing registers as possible, so why does it touch
others at all?  This makes no sense.

Only the backend knows which registers it can write when.


Segher