Re: [boost] Template Instantiation Profiler with Callgrind Output (KCacheGrind)

Subject: Re: [boost] Template Instantiation Profiler with Callgrind Output (KCacheGrind)
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-01-28 01:19:17

On 1/25/2015 8:33 PM, Mikael Persson wrote:
> Hi boost developers and users,
>
> I just wanted to announce a recent development in my little pet-project,
> which is Templight: a template instantiation profiling tool based on Clang.
> I think that many of you would be interested in experimenting with it
> because many boost libraries are great examples of template-heavy libraries
> and many maintainers, developers and users might be interested in gathering
> data and diagnosing the real compilation costs (in time and memory) of
> various components of Boost.
>
> Templight is a Clang-based profiler that can act as a drop-in replacement
> (e.g., in cmake) for the clang compiler, with the addition of generating a
> complete trace of the template instantiation history with associated time
> and memory (optional) costs. This allows you to see not only how deeply
> recursive certain template instantiations are, but also identify which
> instantiations the compiler spends the most time or memory on. It is
> basically to meta-programming what a run-time profiler is to ordinary code.
>
> The templight profiler itself has reached a fairly stable state. It works
> at least under Linux and Windows (through "templight-cl.exe", which is a
> drop-in replacement for "clang-cl.exe", which is compatible with MSVC
> "cl.exe"), but probably works wherever clang works. Which means that you
> are welcome to try it. I have also used it successfully to build a few
> cmake-based projects (by setting CC and CXX environment variables to point
> to templight). Templight is currently also used in the back-end of the
> "metashell" project as well (an interactive shell interpreter and debugger
> for C++ template meta-programs). You can build the templight profiler
> against the clang source (with a patch + some added code), as it instructs
> on the github readme:
>
> https://github.com/mikael-s-persson/templight

What is to keep clang from changing the files which templight patches or 
the llvm/tools/clang/tools/CMakeLists.txt which I am instructed to 
manually change. Is there a valid place to further discuss templight if 
I have problems ?

>
> But most recently, I have created a separate set of tools to convert
> templight trace files to other formats. The most awesome of these outputs
> is the "callgrind" output, which produces a "meta-"call-graph, that is
> similar to (and in the same format as) call-graphs generated by run-time
> profiling tools like callgrind, but the profiling data is, of course,
> related to the compilation costs (time / memory). That conversion tool is
> available here:
>
> https://github.com/mikael-s-persson/templight-tools
>
> With that, you can open the converted templight trace files in the
> visualization tool KCacheGrind, which is great (works both on unix-like
> systems and Windows, thanks to Qt5). Here is a screenshot of that for one
> of Boost.Container's example programs:
>
> https://raw.githubusercontent.com/mikael-s-persson/templight-tools/master/images/kcachegrind_snap1.png
>
> I really hope that some of you will give this a try. I'm really hoping that
> it will be useful to you, and that you can provide feedback and feature
> requests. I couldn't think of any better target audience for this tool.