> On Aug 6, 2020, at 3:31 AM, Richard Biener <rguent...@suse.de> wrote:
>
> On Wed, 5 Aug 2020, Qing Zhao wrote:
>
>> Hi, Richard,
>>
>> Thanks a lot for your careful review and detailed comments.
>>
>>
>>> On Aug 4, 2020, at 2:35 AM, Richard Biener <rguent...@suse.de
>>> <mailto:rguent...@suse.de>> wrote:
>>>
>>> I have a few comments below - I'm not sure I'm qualified to fully
>>> review the rest though.
>>
>> Could you let me know who will be the more qualified person to fully review
>> the rest of middle-end change?
>
> Jeff might be, but with the intended purpose (ROP mitigation AFAIU)
> it would be nice for other target maintainers to chime in (Segher for
> power maybe) for the question below...
>
>>>>>>> + if (!targetm.calls.zero_call_used_regno_p (regno, gpr_only))
>>>>>>> + continue;
>>>
>>> Why does the target need some extra say here?
>>
>> Only target can decide which hard regs should be zeroed, and which hard regs
>> are general purpose register.
>
> I'm mostly questioning the plethora of target hooks added and whether
> this details are a good granularity applying to more than just x86.
> Did I suggest to compute a hardreg set that the middle-end says was
> used and is not live and leave the rest to the target?
Yes, I agree that there might be too much details exposed to middle-end in the
current design.
A single target hook as you suggested:
targetm.calls.zero_regs (used-not-live-hardregset, gpr_only);
Might be a cleaner design.
Thanks.
Qing
