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

[Qing Zhao]

Hi, Alexandre,

CC’ing Richard for his comments on this.


> On Aug 10, 2020, at 9:39 PM, Alexandre Oliva <oliva@adacore.com> wrote:
>> I think that moving how to zeroing the registers part to each target
>> will be a better solution since each target has
>> Better idea on how to use the most efficient insns to do the work.
> 
> It's certainly good to allow machine-specific optimized code sequences,
> but it would certainly be desirable to have a machine-independent
> fallback.  It doesn't seem exceedingly hard to loop over the registers
> and emit a (set (reg:M N) (const_int 0)) for each one that is to be
> zeroed out.

The current implementation already includes such machine-independent code, it should be very easy to add this.

Richard, what’s your opinion on this?
Do we need a machine-independent implementation to zeroing the registers for the default when the target does not provide a optimized
Implementation?

Thanks.

Qing

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