Improved recompilation times by utilizing CCache.

[KOLANICH]

Utilizing CCache is especially useful when one realizes he misses a feature and so recompiles the tool with that feature enabled. Or when one realizes he has accidentially enabled a feature unavalable on his platform, so compilation fails and one has to recompile. In that case without CCache CMake has to cause recompile from scratch since it alters the preprocessor. CCache is capable to detect the recompilation from scratch is not needed and to reuse the suitable artifacts from previous builds.

[tkonolige]

Hi @KOLANICH, thanks for submitting a PR!

Historically, we did have ccache enabled by default if it was installed. I think there were some issues with using ccache with hexagon, so it was disabled in #11189. If you want to use cmake with your builds you can run cmake -DCMAKE_CXX_COMPILER_LAUNCHER=ccache ... when you configure cmake. If you'd like to try and get it enabled by default for everyone using TVM, you can try adding these lines https://github.com/apache/tvm/pull/11189/files#diff-1e7de1ae2d059d21e1dd75d5812d5a34b0222cef273b7c3a2af62eb747f9d20aL769-L796 back in and seeing if hexagon will still build.

[tkonolige]

Actually I've created a PR to re-enable ccache here: #12839

[KOLANICH]

If you want to use cmake with your builds you can run cmake -DCMAKE_CXX_COMPILER_LAUNCHER=ccache ... when you configure cmake.

I have tried this first (but not when configuring, I have edited using cmake-gui), but I got some errors of interaction between CMake and ninja (that have forced me into cleaning CMake cacheand starting from scratch several times), so I resorted to this way.

Actually I've created a PR to re-enable ccache here: #12839

Thanks, I have left my comment there.

[KOLANICH]

CMAKE_CXX_COMPILER_LAUNCHER

My bad, I have used CMAKE_CXX_COMPILER + CMAKE_CXX_FLAGS. Thanks for reminding me that var exists.