The repository contains a tool to convert perf.data profile to AutoFDO profile that can be used by GCC and LLVM.
Each compiler is supported by a different tool. For GCC, use
create_gcov. For LLVM, use
create_llvm_prof. LLVM version
5 or higher is required. The two tools have compatible command
line flags. However, the outputs are incompatible. You cannot
use the profile generated for GCC in LLVM and vice-versa.
Prerequisites to Build:
sudo apt-get -y install libtool autoconf automake git libelf-dev libssl-dev pkg-config
Clone & Compile
Clone the repository using the following command:
git clone --recursive https://github.com/google/autofdo.git
Full build instructions are in the INSTALL file, most can just install the above dependencies, and:
aclocal -I .; autoheader; autoconf; automake --add-missing -c ./configure # or --with-llvm=$(which llvm-config-5.0) make
Note: do not use the
-j (parallel build) option of make. The configure scripts
for the sub-projects fail if run in parallel
Depending on your compiler, a perf dump can be collected by running one of:
./create_gcov --binary=BINARY --profile=PERF_PROFILE --gcov=OUTPUT ./create_llvm_prof --binary=BINARY --profile=PERF_PROFILE --out=OUTPUT
--profile: PERF_PROFILE collected using linux perf (with last branch record). In order to collect this profile, you will need to have an Intel CPU that have last branch record (LBR) support. You also need to have your linux kernel configured with LBR support. To profile:
# perf record -c PERIOD -e EVENT -b -o perf.data -- ./command
Note: EVENT is refering to BR_INST_RETIRED:TAKEN if available. For some architectures, BR_INST_EXEC:TAKEN also works.
--binary: BINARY with debug info. You need to make sure the binary name is the same as the binary you run during profiling. Additionally, you will need to have debug info (i.e. line table) availabe in the binary. This means that you need to compile the binary with "-gmlt" or "-g1". For LLVM, you alse need to have -fdebug-info-for-profiling.
For create_gcov: An AutoFDO profile in gcov format. To use the profile with AutoFDO, you need to use the google gcc branch (gcc.gnu.org/svn/gcc/branches/google/gcc-4_8), and pass the following flag to GCC: -fauto-profile=PROFILE_FILE
For create_llvm_prof: An AutoFDO profile in LLVM format. To use the profile with LLVM, you need to use the flag -fprofile-sample-use=PROFILE_FILE. This feature is available in LLVM 3.5 and later.