Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test case

[Wangnan (F)]

On 2016/12/2 23:44, Arnaldo Carvalho de Melo wrote:
> Em Sat, Nov 26, 2016 at 07:03:34AM +0000, Wang Nan escreveu:
> > Add basic clang support in clang.cpp and test__clang() testcase. The
> > first testcase checks if builtin clang is able to generate LLVM IR.
> >
> > tests/clang.c is a proxy. Real testcase resides in
> > utils/c++/clang-test.cpp in c++ and exports C interface to perf test
> > subsystem.
> >
> > Test result:
> >
> >     $ perf test -v clang
> >     51: Test builtin clang support                               :
> >     51.1: Test builtin clang compile C source to IR              :
> >     --- start ---
> >     test child forked, pid 13215
> >     test child finished with 0
> >     ---- end ----
> >     Test builtin clang support subtest 0: Ok
> While testing this I noticed that the perf binary got huge, can't this
> be done in some other way, i.e. using dynamic library?

I intentionally use statically linking because it is good for
smartphone: we can simply 'adb push' a statically linked perf
to Android.

The resulting ELF executable would be even larger if LLVM is
built with default setting.

In my setting the resuling 'perf' is less than 60MB:

 $ ls -s  ~/perf -h
 58M /home/wn/perf

 $ size  ~/perf
   text       data        bss        dec        hex    filename
 56931273    2950808    24108632    83990713    50198b9 /home/wn/perf

It is reasonable for me.

I think using dynamic clang and llvm libraries is possible but I
never tried it before. It depend on LLVM compiling. I think if
distro provides shared libraries then perf can utilize them
automatically. Let me check it today.

About the file size, I discussed with Alexei, he taught me a lot
on it. Maybe he or his ioVisor ex-colleagues can provide some
new idea?

Thank you.