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Re: eliminate dead stores across functions
- From: "Bin.Cheng" <amker dot cheng at gmail dot com>
- To: Martin Jambor <mjambor at suse dot cz>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, Prathamesh Kulkarni <prathamesh dot kulkarni at linaro dot org>, GCC Development <gcc at gcc dot gnu dot org>
- Date: Tue, 6 Mar 2018 16:50:40 +0000
- Subject: Re: eliminate dead stores across functions
- Authentication-results: sourceware.org; auth=none
- References: <CAAgBjMkcuch04W94DB06Vv7oYZQPLk2VRN5ALd_0Vt=CmzZ=-w@mail.gmail.com> <CAFiYyc0ZwKqyfX2hyFS+s7tB=gaEJ5OS1zq6BciDFLnn=ynM3w@mail.gmail.com> <CAHFci2_vzxxtSjzSba7z-HZQJx29zJCWHBTTaQABeEytCa0yCw@mail.gmail.com> <ri64lltf922.fsf@suse.cz>
On Tue, Mar 6, 2018 at 4:44 PM, Martin Jambor <mjambor@suse.cz> wrote:
> Hi Bin,
>
> On Tue, Mar 06 2018, Bin Cheng wrote:
>> On Tue, Mar 6, 2018 at 2:28 PM, Richard Biener
>>>
>>> Do you think the situation happens often enough to make this worthwhile?
>> There is one probably more useful case. Program may use global flags
>> controlling
>> how it does (heavy) computation. Such flags are only set couple of
>> times in execution
>> time. It would be useful if we can (IPA) propagate flags into computation heavy
>> functions by versioning (if necessary). For example:
>>
>> int flag = 1;
>> void foo ()
>> {
>> //heavy computation wrto to flag
>> }
>> void main()
>> {
>> flag = 2;
>> foo();
>> flag = 1;
>> foo();
>> }
>>
>
> So basically IPA-CP done on (not-addressable) static global variables.
> Do you happen to know some real code which would benefit? I'd like to
> experiment with it but would like to have a real thing to look at, as
> opposed to artificial test cases.
As Richi pointed out, I think this is not rare in spec. For this
moment I only vaguely remember 544.nab_r for such issue, but I am sure
there are other cases.
Thanks,
bin
>
> Thanks,
>
> Martin
>
>