[PATCH] D36351: [lld][ELF] Add profile guided section layout

[Rui Ueyama via llvm-commits]

On Mon, Dec 4, 2017 at 2:30 PM, Michael Spencer <bigcheesegs at gmail.com>
wrote:

> I've attached updated patches.
>
> I just tested these patches on Linux based on {llvm, clang, compiler-rt,
> lld} as of r319686 and everything worked just fine with the following steps:
>
> * Applied the patches.
> * Built llvm, clang, compiler-rt and lld in a Release build.
> (cgprofile-build)
> * Built llvm, and lld in a Release build using the clang from
> cgprofile-build with `-fprofile-instr-generate`. (instrumented-build)
> * Ran `check-lld` on instrumented-build
> * Ran `cgprofile-build/llvm-profdata merge <PATH-TO-LLVM-SOURCE>/llvm-
> project/lld/test/ELF/default.profraw -o default.profdata` in the
> instrumented-build directory
>

This step is wrong. `default.profraw` file does not exist in that directory.

After fixing the path, I could follow the next step, but during the build
with profile data, clang crashed.

Looks like we wasted too much time just to reproduce one result on the
other end. I'll write a shell script to do all these steps in a batch
without human interaction so that we don't need to type in the commands by
hand. I'll upload everything to github, so please wait for a while.

* Built llvm, and lld in a Release build using the clang from
> cgprofile-build with `-fprofile-instr-use=default.profdata`.
> (cg-profile-optimized-build)
> * Checked that the .o files from cg-profile-optimized-build had call graph
> profiles using `cgprofile-build/llvm-readobj -elf-cg-profile`
>
> - Michael Spencer
>
> On Mon, Nov 27, 2017 at 9:11 PM, Michael Spencer <bigcheesegs at gmail.com>
> wrote:
>
>> On Mon, Nov 27, 2017 at 9:07 PM, Davide Italiano <davide at freebsd.org>
>> wrote:
>>
>>> Maybe this happens only on Linux? As far as I can tell the patch has
>>> been developed on Windows entirely. Michael, have you tried linux?
>>>
>>
>> It has been tested mostly on Linux.
>>
>> - Michael Spencer
>>
>>
>>>
>>> On Nov 27, 2017 9:05 PM, "Michael Spencer" <bigcheesegs at gmail.com>
>>> wrote:
>>>
>>>> On Mon, Nov 27, 2017 at 5:44 PM, Rui Ueyama <ruiu at google.com> wrote:
>>>>
>>>>> I rebased the patches to HEAD and tried to use it again. When I ran
>>>>> `bin/llvm-profdata merge default.profraw -o default.profdata`, it creates
>>>>> almost empty default.profdata and it shrunk default.profraw. That seems
>>>>> pretty odd to me. Michael, do you know what is going on?
>>>>>
>>>>> Before:
>>>>>
>>>>> -rw-r-----  1 ruiu eng  29M Nov 27 17:39 default.profraw
>>>>>
>>>>> After:
>>>>>
>>>>> -rw-r-----  1 ruiu eng  560 Nov 27 17:39 default.profdata
>>>>> -rw-r-----  1 ruiu eng 2.2M Nov 27 17:39 default.profraw
>>>>>
>>>>> The rebased patch is available at https://reviews.llvm.org/D40534.
>>>>>
>>>>
>>>> I'm not sure what the issue is without more information. My patch
>>>> doesn't change how llvm profile information works, it only uses the data.
>>>>
>>>> - Michael Spencer
>>>>
>>>>
>>>>>
>>>>> On Mon, Nov 27, 2017 at 2:01 PM, Davide Italiano <davide at freebsd.org>
>>>>> wrote:
>>>>>
>>>>>> On Mon, Nov 27, 2017 at 1:49 PM, Rui Ueyama <ruiu at google.com> wrote:
>>>>>> > I'm so sorry that I didn't respond in a timely manner. I'm reading
>>>>>> it again
>>>>>> > now.
>>>>>> >
>>>>>>
>>>>>> No worries, definitely not your fault. The whole back and forth has
>>>>>> been a little slow, but this has been around for almost 6 months now
>>>>>> (and has been in development for much longer) so we should really
>>>>>> decide whether we want to ship it or kill it :)
>>>>>>
>>>>>
>>>>>
>>>>
>>
>
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