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

[Kristóf Umann via llvm-dev]

Actually, there is still one thing I seem to be having trouble with, which
is compiling clang with compiler-rt: Targets for libclang_rt are generated
as normal, but not when I specify LLVM_PROFDATA_FILE. Looking at the cmake
output, every COMPILER_RT_* test fails. Is PGO and building compiler-rt
mutually exclusive?

On Tue, 3 Sep 2019 at 19:43, Kristóf Umann <dkszelethus at gmail.com> wrote:

> 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 I've quickly learned that its outdated, because the script it talks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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