hoangt/llvm-tracer

An LLVM pass to profile dynamic LLVM IR instructions and runtime values

LLVM IR Trace Profiler (LLVM-Tracer) 1.1 Public Release

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

============================================ Requirements:

LLVM 3.4.0 and Clang 3.4.0 64-bit

Build:

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
   

Run:

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

Example program: triad

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

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Emma Wang and Sophia Shao

Harvard University, 2014