[llvm-dev] Android kernel PGO with LLVM

Xinliang David Li via llvm-dev llvm-dev at lists.llvm.org
Tue Apr 28 10:08:45 PDT 2020

The entry point  is for value profiling and should be defined in
InstrProfilingValue.o in the archive library. Can you check the symbol
table of the .a file?


On Tue, Apr 28, 2020 at 4:25 AM Yi Ma via llvm-dev <llvm-dev at lists.llvm.org>

> Hello,
> I'm working on Android kernel profile-guided optimization to figure out
> whether pgo can improve the performance of Android kernel. I have tried
> to added '-fprofile-generate' option to build Android kernel(msm-4.19).
> But error occurs during building: "undefined reference to
> '__llvm_profile_instrument_target'".
> I have tried to add libclang_rt.profile-aarch64-android.a as a library
> when building Android kernel, but the error still shows up. I think the
> kernel may not be able to call libraries outside the kernel source tree,
> so I was porting pgo-related files(compiler-rt/lib/profile/) from
> compiler-rt to Android kernel source tree.
> Do you know why did this error occurs? And am I doing the right thing?
> Is it possible to improve the performance of Android kernel with llvm
> pgo mechanism?
> Thanks,
> Yi Ma
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