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

[Segher Boessenkool]

On Tue, Sep 15, 2020 at 08:51:57PM -0500, Qing Zhao wrote:
> > On Sep 15, 2020, at 6:09 PM, Segher Boessenkool <segher@kernel.crashing.org> wrote:
> > If you want the zeroing insns to stay with the return, you have to
> > express that in RTL.  
> 
> What do you mean by “express that in RTL”?
> Could you please explain this in more details?

Exactly as I say: you need to tell in the RTL that the insns should stay
together.

Easiest is to just make it one RTL insn.  There are other ways, but
those do not help anything here afaics.

> Do you mean to implement this in “targetm.gen_return” and “targetm.gen_simple_return”?

That is the easiest way, yes.

> > Anything else is extremely fragile.


Segher