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Re: ARM calling conventions generated in gcc with different optimizations
- From: Vasily Golubev <vasily dot golubev at gmail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Mon, 23 Sep 2013 19:23:32 +0400
- Subject: Re: ARM calling conventions generated in gcc with different optimizations
- Authentication-results: sourceware.org; auth=none
- References: <CAGKFyZ75=Ws4Nq1-1PgBedw7vdTLwrhY7gMzsB8iWbBbq4+Ugw at mail dot gmail dot com> <CAJA7tRaGB6zwx2yivHmo-wcKqHhM_SjZ7VV=JUh-xX+YSJjBRQ at mail dot gmail dot com>
Thank you a lot for your answer, Mr. Radhakrishnan!
I think it was my mistake to use phrase "I will save LR at some
place"... I mean I can catch the first instruction of any function
precisely. And save LR value at that time to my local storage. And I
also can catch the first instruction after exit from any function
precisely. And will compare the address of this instruction with
stored LR.
So, is it possible for gcc to generate code that will not save return
address in LR before some call on ARM? Or it is forbidden?
Vasily
On Mon, Sep 23, 2013 at 7:07 PM, Ramana Radhakrishnan
<ramana.gcc@googlemail.com> wrote:
>> And my main question is it possible to rely on this fact when
>> compiling with gcc and different levels of optimizations?
>
> No it is not , the compiler (especially trunk) is free to use LR as a
> temporary after epilogue has been generated at higher optimization
> levels.
>
>
>> Is it
>> possible to generate some straightforward heuristic to detect this
>> evens (with\without debug info)?
>
> With debug information you could in theory work this out but not
> without it especially if LR were used as a temporary.
>
> regards
> Ramana
>
>
>>
>> Thank you in advance for any suggestions!
>>
>> --
>> Best Regards,
>> Vasily
--
Best Regards,
Vasily