Re: RFC: New userspace fetch/store API

[Jason Thorpe <thorpej%me.com@localhost>]

> On Feb 25, 2019, at 9:18 AM, Andrew Cagney <andrew.cagney%gmail.com@localhost> wrote:
> 
> So the out-of-band error check becomes the slooooow memory write?
> I don't see it as a problem as the data would presumably be written to
> the write-back cached's stack (besides, if the function is short, LTO
> will eliminate it).
> 
> FWIW, I suspect the most "efficient" way to return the value+error as
> a struct - ABIs would return the pair in registers or, failing that,
> pass a single stack address - but I don't think this interface should
> go there.

Agreed, this is way off in the weeds of “premature optimization”.  Besides, why make this function “weird” compared to everything else that just returns an error code in a normal way?

-- thorpej