cppcon2017

Optimizing compilation times of Generated Code with Templates

Requirements:

• Clang requirements: https://llvm.org/docs/GettingStarted.html#requirements
• Ninja build system: https://ninja-build.org/

Build the tools:

• ./tools/build_deps.sh

This will download, patch, and build clang, llvm, and templight.

What do the patches include?

Time Report:

These patches add modifications to Clang's frontend to gather more metrics on compilation times

• Template Instatiation Time: https://reviews.llvm.org/D36946
• Preprocessing Time (Lex) (author @Brian Gesiak): https://reviews.llvm.org/D36492

Templight:

• Capture template instantiations to gather data on instantiation times. Original Project: https://github.com/mikael-s-persson/templight

Tools:

• Convert profiled template instantitations into a nice list showing instantitation time per template: https://github.com/eduardo-elizondo/templight-tools

How to use:

If you have CMake follow: example/CMakeLists.txt

Time Report:

• ./external/llvm_build/bin/clang++ -ftime-report a.cpp

Templight:

• ./external/llvm_build_bin/templight++ -Xtemplight -profiler -Xtemplight -ignore-system -c a.cpp
• ./tools/get_inst_times.sh results your_build/file.cpp.o.trace.pbf

For more flags that you can use for templight, visit the github in the Requirement section. In general, "profiler" and "ignore-system" have been the most useful ones.

Questions?

Please create a github issue and we can start a discussion!