Re: [PATCH zero-call-used-regs] Add leafy mode for zero-call-used-regs

[Qing Zhao <qing.zhao@oracle.com>]

Hi, Alexandre,


> On Jun 21, 2023, at 9:16 PM, Alexandre Oliva <oliva@adacore.com> wrote:
> 
> Hello, Qing,
> 
> On Jun 16, 2023, Qing Zhao <qing.zhao@oracle.com> wrote:
> 
>> As I mentioned in the previous round of review, I think that the documentation
>> might need to add more details on what’s the LEAFY mode,
>> The purpose of it, and how to use it, provide more details to the end-users.
> 
> I'm afraid I'm having difficulty picturing what it is that you're
> looking for.  The proposal incorporates, by reference, all the
> documentation for 'used' and for 'all', and the way to use it is no
> different.
> 
>>> +Same as @samp{used} in a leaf function, and same as @samp{all} in a
>>> +nonleaf function.

Oh, yeah.  The definition of “leafy” is here. -:)

It’s better to add this definition earlier in the list of the “three basic values”, to make it “four basic values”, like the following:

=======
In order to satisfy users with different security needs and control the
run-time overhead at the same time, the @var{choice} parameter provides a
flexible way to choose the subset of the call-used registers to be zeroed.
The four basic values of @var{choice} are:

@itemize @bullet
@item
@samp{skip} doesn't zero any call-used registers.

@item
@samp{used} only zeros call-used registers that are used in the function.
A ``used'' register is one whose content has been set or referenced in
the function.

@item
@samp{all} zeros all call-used registers.
@end itemize

@item
@samp{leafy} Same as @samp{used} in a leaf function, and same as @samp{all} in a
    nonleaf function. This value is mainly to provide users a more efficient mode to zero 
    call-used registers in leaf functions.
@end itemize
======

Then,  in the full list of choice, add the new values of leafy, leafy-gpr, leafy-arg, leafy-gpr-arg 

The sentence "This value is mainly to provide users a more efficient mode to zero 
    call-used registers in leaf functions.” just for your reference,  the wording can certainly be improved.  -:)
> 
> If there was documentation on how to choose between e.g. all and used, I
> suppose I could build on that to add this intermediate choice, but...  I
> can't find any such docs, and I'm uncertain on whether adding that would
> be useful to begin with.
> 
> Did you have something else in mind?


Hope this time I am clear (and sorry for the confusion in the previous emails).

thanks.

Qing

> 
> -- 
> Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
>   Free Software Activist                       GNU Toolchain Engineer
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