Disables link-time optimization unless -DENABLE_LTO=ON is passed. #3524
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This disables the `-flto` LTO flag by default since we're seeing segfaults in compiler lto plugins, binutils and linker errors again and again for various clang / gcc / binutils combinations. Pass `-DNEBALE_LTO` to `cmake` in order to re-enable LTO. LTO situation in short: - LTO does not work at all for gcc<4.9 - With gcc>=4.9 the "slim" LTO format is getting used dumping IR - Older binutils need LTO plugins which know how to read this IR - Recent binutils handle this format all by themselves - LLVM is more or less the same with some Clang versions segfaulting If you need the performance benefit of LTO, make sure your compiler and binutils are up to date and see for yourself if LTO builds work for you. References: - https://gcc.gnu.org/wiki/LinkTimeOptimizationFAQ - #3481 (comment) - #3501 - #3441 (and a ton of other LTO tickets if you search for them)
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Which downstream projects relied on this default and have to be updated now? |
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@daniel-j-h |
daniel-j-h
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Jan 5, 2017
The default just flipped from on to off upstream. Re-enables LTO. See Project-OSRM/osrm-backend#3524.
TheMarex
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Jan 5, 2017
TheMarex
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Jan 18, 2017
The default just flipped from on to off upstream. Re-enables LTO. See Project-OSRM/osrm-backend#3524.
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This disables the
-fltoLTO flag by default since we're seeingsegfaults in compiler lto plugins, binutils and linker errors again and
again for various clang / gcc / binutils combinations.
You can pass
-DNEBALE_LTOtocmakein order to re-enable LTO.LTO situation in short:
If you need the performance benefit of LTO, make sure your compiler and
binutils are up to date and see for yourself if LTO builds work for you.
References:
(and a ton of other LTO tickets if you search for them)