Re: [google/autofdo] how to use this tools for autoLIPO（autoFDO + LIPO）in gcc google 4_9 branch ? (#106)

Re: [google/autofdo] how to use this tools for autoLIPO（autoFDO + LIPO）in gcc google 4_9 branch ? (#106)

[ijinma]

hi, Wei


   I'm so honored to have your answer to my question. Although the llvm thin LTO has a great advantage, I still want to try autoLIPO on GCC. I read the source code of the autoFDO tool briefly, but unfortunately I didn't find a way to enable autoLIPO, even as you say the config doesn't work anymore.  


   I want to recreate your work, and I think it's worth continuing on gcc. I think there should be a proper way to turn on autoLIPO, though it might be very old. But I'm a beginner in the compiler direction, and I'm not good at all of this.


   So could you give me some help?


   1. GCC ([google gcc_4.8 ?](https://chromium.googlesource.com/chromiumos/third_party/gcc/+/refs/heads/svn-mirror/google/gcc-4_8)) and autoFDO versions that have been successfully run by autoLIPO, or some suggestions.


   2. The usage or description of autoFDO enabling auxiliary module. That is, the imports file generated by AutoFDO stores the grouping algorithm result of the LIPO module.


   3. Or what would I need to do if I wanted to successfully use autoLIPO on GCC?
   Looking forward to your reply!


  thanks，
  ijinma
On 2/19/2021 11:31，Dehao Chen<notifications@github.com> wrote：

Hi ijinma,

We stop supporting autoFDO + LIPO for a long time. The last version of gcc
in google branch which we know autoFDO + LIPO would work was gcc-4.8. After
that we move to llvm. The tool has gone through many changes and we never
test those changes with autoFDO + LIPO, so it is very possible that the
config doesn't work anymore. Sorry about that.

Thanks,
Wei.

On Thu, Feb 18, 2021 at 7:12 PM Dehao Chen <dehao@google.com> wrote:

> +Wei Mi <wmi@google.com>
>
> On Thu, Feb 18, 2021 at 7:05 PM jinam <notifications@github.com> wrote:
>
>> hi, @danielcdh <https://github.com/danielcdh>
>> I recently read the code of LIPO
>> <https://gcc.gnu.org/wiki/LightweightIpo> (Profile Feedback Based
>> Lightweight IPO) in gcc and find that the theory is very good. In this
>> paper <https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7559528>,
>> I see that LIPO has realized the combination with autoFDO, avoiding the
>> disadvantage of LIPO having to recompile the FDO process.
>>
>> I tried to use the autoFDO tool to generate the gcda and imports files required by LIPO, and although imports were automatically generated, it was always empty, causing LIPO not to optimize the program.
>>
>>
>> Therefore, I want to know how to make the imports file generated by the
>> autoFDO tool have content instead of empty and make LIPO effective.
>>
>> thanks，
>> ijinma
>>