LLVM-Tracer is an LLVM instrumentation pass to print out a dynamic LLVM IR trace, including dynamic register values and memory addresses.

If you use LLVM-Tracer in your research, please cite:

ISA-Independent Workload Characterization and its Implications for Specialized Architectures, Yakun Sophia Shao and David Brooks, International Symposium on Performance Analysis of Systems and Software (ISPASS), April 2013

LLVM 3.4.0 and Clang 3.4.0 64-bit

1. Set LLVM_HOME to where you installed LLVM Add LLVM and Clang binary to your PATH:

   export $LLVM_HOME=/path/to/your/llvm/installation
   export $PATH=$LLVM_HOME/bin:$PATH
   export $LD_LIBRARY_PATH=$LLVM_HOME/lib/:$LD_LIBRARY_PATH
   

2. Go to where you put LLVM-Tracer source code

   cd /path/to/LLVM-Tracer/full-trace/
   make
   cd /path/to/LLVM-Tracer/profile-func/
   make
   

After you build LLVM-Tracer, you can use example triad programs in the example directory to test LLVM-Tracer.

1. Go to /your/path/to/LLVM-Tracer/example/triad

2. Run LLVM-Tracer to generate a dynamic LLVM IR trace a. LLVM-Tracer tracks regions of interest inside a program. In the triad example, we want to analyze the triad kernel instead of the setup and initialization work done in main. To tell LLVM-Tracer the functions we are interested, set enviroment variable WORKLOAD to be the function names (if you have multiple functions interested, separated by comma):

   export WORKLOAD=triad export WORKLOAD=md,md_kernel

   b. Generate LLVM IR:

   clang -g -O1 -S -fno-slp-vectorize -fno-vectorize -fno-unroll-loops -fno-inline -emit-llvm -o triad.llvm triad.c

   c. Run LLVM-Tracer pass: Before you run, make sure you already built LLVM-Tracer. Set $TRACER_HOME to where you put LLVM-Tracer code.

   export TRACER_HOME=/your/path/to/LLVM-Tracer opt -S -load=$TRACER_HOME/full-trace/full_trace.so -fulltrace triad.llvm -o triad-opt.llvm llvm-link -o full.llvm triad-opt.llvm $TRACER_HOME/profile-func/tracer_logger.llvm

   d. Generate machine code:

   llc -filetype=asm -o full.s full.llvm gcc -fno-inline -o triad-instrumented full.s

   e. Run binary. It will generate a file called dynamic_trace under current directory.

   ./triad-instrumented

   f. We provide a python script to run the above steps automatically for SHOC.

   cd /your/path/to/LLVM-Tracer/triad export TRACER_HOME=/your/path/to/LLVM-Tracer python llvm_compile.py $TRACER_HOME/example/triad triad

Emma Wang and Sophia Shao

Harvard University, 2014