[LLVMdev] Questions about LLVM PGO and autoFDO

[Diego Novillo]

On Mon, May 12, 2014 at 12:59 PM, 猫妖 <spcatman at qq.com> wrote:

>   2. Problems in autoFDO:
>   Actually the problem happened in using create_llvm_prof, transformation is
> failed.
>   clang -O2 -g test.c -o a.out
>   perf record -b ./a.out    (perf version is 0.0.2, "-b" option is not
> recognized, why?)
>   change to: perf record ./a.out   (so perf.data is generated)
>   create_llvm_prof --binary=./a.out --out=code.prof  (it read a.out and
> perf.data)
>   error: Malformed .note.gnu.build-id section
>            no build id found in the binary
>   it seems that a.out has no build id.

This error message from create_llvm_prof is actually harmless. Dehao
will be removing it at some point. The file code.prof should have
content and clang will be able to read it. Please try:

$ clang -fprofile-sample-use=code.prof -g ...


Diego.