Tau clang plugin

Use

The aim of this plugin is to facilitate the use of TAU. Parsing a function-listing file, the TAU plugin runs a function pass on each function from the original source, adding them to be instrumented if the function-listing file specifies it.

Compilation and installation

As TAU relies on LLVM's Intermediate Representation, the TAU plugin is built upon an LLVM installation. That means an LLVM install is needed, as well as a TAU install.

Note: LLVM and the TAU plugin must be compiled using the same compilers.

TAU installation

TAU installation is done by following these commands:

git clone https://github.com/UO-OACISS/tau2.git

cd tau2

./installtau -cc=clang -c++=clang++ -dwarf=download -bfd=download -iowrapper -iowrapper -otf=download

TAU records all configurations used to install it in the .allconfigs file. The last used configuration is stored in the .lastconfig file.

LLVM installation

LLVM's installation can be done by following these commands:

git clone https://github.com/llvm/llvm-project.git

cd llvm-project/llvm

mkdir build; cd build

cmake ../../llvm -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PWD/../install -DLLVM_ENABLE_PROJECTS="clang;mlir;polly;flang;libcxx;libcxxabi"

make -j install

Miscellaneous issues and solutions

• On x86 architectures, LLVM 8 needs the following lines to be added to llvm-project/llvm/include/llvm/Demangle/MicrosoftDemangleNodes.h  :

#include <cstdint>

#include <string>

• On PowerPC architectures, all LLVM versions prior to LLVM 9 (included) need to update the file llvm-project/clang/lib/Lex/Lex.cpp from !vec_any_eq(*(const vector unsigned char*)CurPtr, Slashes)) to !vec_any_eq(*(const __vector unsigned char*)CurPtr, Slashes))

• On Aarch64 architectures, to build LLVM 7, it is needed to replace #ifdef __FLT16_MANT_DIG__ by #ifdef __STDC_WANT_IEC_60559_TYPES_EXT__ in the the following files: llvm-project/libcxx/include/type_traits and llvm-project/libcxx/test/libcxx/type_traits/is_floating_point.pass.cpp

Plugin installation

With LLVM installed, the plugin can be built upon it:

git clone https://github.com/coti/tau-llvm-plugin.git

cd tau-llvm-plugin

mkdir build; cd build

cmake .. -DCMAKE_INSTALL_PREFIX=$PWD/../install -DLLVM_ROOT=/PATH/TO/LLVM/INSTALLATION/install

make -j install

Running it

The TAU plugin is a function pass, meaning it takes effect during the compilation of the executable to be instrumented. To do so, the compiling command resembles this:

/PATH/TO/LLVM/INSTALLATION/install/bin/clang -fplugin=/PATH/TO/PLUGIN/INSTALLATION/install/lib/TAU_Profiling.so -mllvm -tau-input-file=/PATH/TO/FUNCTION/LISTING/FILE/select.tau -ldl -L/PATH/TO/TAU/lib/SPECIFIC_TAU_INSTALLATION -lTAU -Wl,-rpath,/PATH/TO/TAU/lib/SPECIFIC_TAU_INSTALLATION -lm [project files]

That being done, execute the code by calling:

tau_exec -T clang,serial ./a.out

Then, to access the instrumentation results, call:

pprof

Packaging

Mac OS

brew install --build-from-source llvm