Undefined symbols when using ThinLTO + cs-profile-generate

[tru]

This is my simple compile script. CC is clang-cl.exe, LD is lld-link.exe and PROFILE is the path to clang_rt.profile.lib

%CC% /c /Fotest_pgo.obj -fprofile-generate=pgo.profraw -flto=thin test.cpp
%LD% /out:test_pgo.exe test_pgo.obj %PROFILE%

.\test_pgo.exe
%PD% merge -o default.prof pgo.profraw

%CC% /c /Fotest.obj -fcs-profile-generate -fprofile-use=default.prof -flto=thin test.cpp
%LD% /out:test.exe test.obj %PROFILE% /lto-cs-profile-generate

This leads to the following error:

lld-link: error: undefined symbol: __llvm_profile_counter_bias
>>> referenced by clang_rt.profile.lib(InstrProfilingFile.c.obj):(mmapForContinuousMode)

In another project I also see that __llvm_profile_filename is undefined.

I tired to define these in the source but it doesn't seem to make a difference.

Anyone using CS PGO on Windows? @zmodem @teresajohnson

[teresajohnson]

@xur-llvm who is the expert on CSPGO
We don't use CSPGO on Windows though. But it sounds like something isn't getting correctly defined in the Windows profile runtime?

[tru]

There is some Windows specific code for this here it seems like - but I am unsure how it's supposed to work: https://github.com/llvm/llvm-project/blob/main/llvm/lib/ProfileData/InstrProf.cpp#L1549

[Andarwinux]

The same problem also happens on MinGW. If I move the definition of INSTR_PROF_PROFILE_NAME_VAR from InstrProfilingNameVar.c back into InstrProfiling.c, the problem will no longer exist.

[tru]

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