Use precompiled headers for building libHalide#8999
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alexreinking wants to merge 5 commits intomainfrom
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Use precompiled headers for building libHalide#8999alexreinking wants to merge 5 commits intomainfrom
alexreinking wants to merge 5 commits intomainfrom
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Windows doesn't like the HALIDE_EXPORT declarations in Error.h Meanwhile, there's all kinds of weird ODR issues cropping up elsewhere. Sigh -- I'll revisit after FetchContent is excised. |
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The implementation here is pretty ugly because everything is just dumped into one big folder. If we had another subfolder for the LLVM-privileged sources, it would be easier to isolate the build rules. |
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@mcourteaux and @abadams -- could I ask you to build locally with this branch and see if it makes a measurable difference for you versus main? |
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After meeting with @abadams, it seems that this is a net slowdown on highly multicore systems. Because of the lack of CI improvement, the inconsistency of results, and the implementation complexity, I'm closing this PR. |
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This PR introduces PCH support for building libHalide. It divides the sources into LLVM and non-LLVM parts; the former additionally precompiling our
LLVM_Headers.hheader.On my MacBook Pro M3 Max, this halves the compilation time from 50s to 25s on 18 threads. I hope this will bring a significant improvement to CI, too.
In terms of total CPU time, I observed 1158s before this PR and 607s after, for a 48% net reduction in compilation time. Using Clang's
-ftime-reportsuggests that header parsing now accounts for only 27% (down from 63!) of the compilation time. Templates take 242s (40%) and the rest of the time is spent in the backend (200s / 33%).