[llvm-dev] [cfe-dev] Clang executable sizes and build stats

[Greg Bedwell via llvm-dev]

Thanks.  We see that reduction too in our clang.exe builds on Windows.
Nice to see that we can make at least some difference!

-Greg

On 22 March 2018 at 04:28, Craig Topper <craig.topper at gmail.com> wrote:

> I just knocked ~400k off the size of the x86 scheduler tables by reducing
> from 5k+ entries to 2k+ entries per cpu.
>
> ~Craig
>
> On Tue, Mar 20, 2018 at 6:34 PM, Andrew Trick <atrick at apple.com> wrote:
>
>>
>>
>> On Mar 17, 2018, at 4:04 PM, Craig Topper via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>> I'm sure the x86 scheduler models are causing bloat. Every time a single
>> instruction appears on a line by itself like this in a scheduler model:
>>
>> def: InstRW<[SBWriteResGroup2], (instregex "ANDNPDrr")>;
>>
>> It causes that instruction to be its own group in the generated output.
>> And its replicated for each CPU. We should look into better using regular
>> expressions or taking advantage of the fact that InstRW can take a list of
>> instructions. That makes those instructions part of a single group and the
>> tablegen backend will only split the group if two CPUs have different
>> ports, latency, etc. for instructions within the group.
>>
>> ~Craig
>>
>>
>> The tables themselves are compact. There’s actually a lot of complexity
>> spent on compacting the resource and latency tables. But, yes, there are
>> 5k+ entries per cpu, roughly 28 byte each. However, if you're looking at a
>> debug build, the tables will be huge. The scheduling class names are much
>> bigger than the data.
>>
>> -Andy
>>
>> On Sat, Mar 17, 2018 at 6:26 AM, Greg Bedwell via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>> Thanks for raising this. This is something we've recently been looking
>>> at too at Sony, as over the course of PS4's lifetime so far we've seen our
>>> clang executable on Windows approximately double in size, which isn't ideal
>>> for things like distributed build systems.  A graph of clang.exe size on
>>> our internal staging branch matches yours closely with it being more of a
>>> death by a thousand cuts rather than being down to a small number of sudden
>>> big-bang changes.
>>>
>>> I did spot one range of about 25 upstream commits in our data where the
>>> exe size increased by over 1MB. My prime suspect in that range was a new
>>> scheduling model being added to the X86 backend but I've not bisected
>>> further to be sure yet.  This would be an interesting case for us as we
>>> don't really need to support any models other than Jaguar for our users but
>>> don't want to break the LLVM tests, nor introduce loads of private changes
>>> to our branch.
>>>
>>> I know our test/QA team have been doing some analysis using Bloaty
>>> McBloatFace to see exactly where the size is coming from and produced some
>>> really nice visualizations of that data.  They've also been looking at how
>>> the MinSizeRelease config does on Windows. I think the size savings were
>>> decent but I'm not sure of performance numbers, if they have any yet.
>>>
>>> I'll ask around at what we have to share once back in the office.
>>>
>>> Thanks for sharing your data!
>>>
>>> -Greg
>>>
>>>
>>>
>>> On Sat, 17 Mar 2018 at 12:36, Dimitry Andric via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I recently did a run where I built clang executables on FreeBSD
>>>> 12-CURRENT [1], from trunk r250000 (2015-10-11) all through r327700
>>>> (2018-03-16), with increments of 100 revisions.  This is mainly meant as an
>>>> archive, for easily doing bisections, but there are also some interesting
>>>> statistics.
>>>>
>>>> From r250000 through r327700:
>>>> * the total (stripped) executable size grew by approximately 43%
>>>> * the size of the text segment grew by approximately 41%
>>>> * the size of the data segment grew by approximately 61%
>>>> * the size of the bss segment grew by approximately 185%
>>>> * real build time (on a 32 core system) grew by approximately 60%
>>>> * user build time (on a 32 core system) grew by approximately 62%
>>>> * maximum resident set size (RSS) grew by approximately 32%
>>>>
>>>> Google spreadsheet with more numbers and some graphs:
>>>>
>>>>
>>>> https://docs.google.com/spreadsheets/d/e/2PACX-1vSGq1U7j45JNC_bcG4HV3jKOV4WBUPbTSgMMFXd5SD0IEPTAFwWnlU2ysprmnHsNe5WONRCjg8F5mHK/pubhtml
>>>>
>>>> -Dimitry
>>>>
>>>> [1] These were built using the "ninja clang clang-headers" target,
>>>> followed by "ninja install-clang install-clang-headers".
>>>>
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>>>>
>>>
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