[llvm-dev] Struggling with a PGO build of clang -- llvm-profdata was built without zlib support?

[Kristóf Umann via llvm-dev]

Yes, that was it! Now that I took a closer look, the guide also states that
I should use the stage2 build. Silly me.

Thanks!

On Tue, 3 Sep 2019 at 19:31, David Blaikie <dblaikie at gmail.com> wrote:

> I /guess/ you actually want /path/to/release_build/llvm-profdata because
> the profiles are generated from binaries compiled with the release build,
> so it's the release build that matters for all things profiling related, I
> would think, in your situation.
>
>
> On Tue, Sep 3, 2019 at 10:06 AM Kristóf Umann via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi!
>>
>> I'm trying to build a fast Clang for myself to use for debug builds on
>> Clang itself, but I've been struggling for a very long time on it. Could
>> you please help?
>>
>> I've been following this guide:
>> https://llvm.org/docs/HowToBuildWithPGO.html
>>
>> I've quickly learned that its outdated, because the script it talks about
>> doesn't work with the monorepo layout at all, but in any case, it does
>> describe how to do the entire process by hand, so I went for that. Here are
>> my steps:
>>
>> * Built a release version of LLVM/Clang/LLD/compiler-rt on version
>> 9.0.0-rc3
>>
>> * Built an instrumented clang with the following config:
>> cmake -G Ninja ../llvm \
>>   -DLLVM_ENABLE_PROJECTS='clang;compiler-rt' \
>>   -DLLVM_TARGETS_TO_BUILD=X86 \
>>   -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
>>   -DCMAKE_CXX_COMPILER=/path/to/release_build/bin/clang++ \
>>   -DCMAKE_C_COMPILER=/path/to/release_build/bin/clang \
>>   -DLLVM_USE_LINKER=/path/to/release_build/bin/ld.lld \
>>   -DLLVM_CCACHE_BUILD=ON \
>>   -DLLVM_BUILD_INSTRUMENTED=IR \
>>   -DLLVM_BUILD_RUNTIME=No \
>>   -DLLVM_ENABLE_ZLIB=1 \
>>   -DCMAKE_BUILD_TYPE=Release \
>>   -DLLVM_ENABLE_LTO=Thin \
>>   -DCMAKE_RANLIB=/path/to/release_build/bin/llvm-ranlib \
>>   -DCMAKE_AR=/path/to/release_build/bin/llvm-ar
>>
>> I tried this without specifying zlib being enabled, without thinlto,
>> everything I could come up with really.
>>
>> * Built a debug Clang with the following configuration:
>> cmake -G Ninja ../llvm \
>>   -DCMAKE_BUILD_TYPE=Debug \
>>   -DLLVM_ENABLE_PROJECTS='clang' \
>>   -DBUILD_SHARED_LIBS=ON \
>>   -DLLVM_TARGETS_TO_BUILD=X86 \
>>   -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
>>   -DCMAKE_CXX_COMPILER=/path/to/instrumented_build/bin/clang++ \
>>   -DCMAKE_C_COMPILER=/path/to/instrumented_build/bin/clang \
>>   -DLLVM_USE_LINKER=/path/to/release_build/bin/ld.lld  \
>>   -DLLVM_CCACHE_BUILD=ON
>>
>> * Tried to use /path/to/instrumented_build/llvm-profdata on the profraw
>> files found in  /path/to/instrumented_build/profiles/.
>>
>> I got the following error message:
>> error: profiles/default_15822678447050577402_0.profraw: Profile uses zlib
>> compression but the profile reader was built without zlib support
>>
>> Even when I explicitly specified zlib to be enabled, and double check
>> whether zlib.h was found I got this message. I've found this [1] thread
>> mentioning a similar issue, but I'm unfortunately not familiar enough with
>> LLVM itself to use the discussed tips with any success. Is there something
>> obvious I'm missing?
>>
>> Thanks in advance,
>> Kristóf
>>
>> [1] http://lists.llvm.org/pipermail/llvm-dev/2017-July/115588.html
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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