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Stabilizer: Statistically Rigorous Performance Evaluation

Charlie Curtsinger and Emery D. Berger

Copyright (C) 2013 University of Massachusetts Amherst


Stabilizer is a compiler transformation and runtime library for dynamic memory layout randomization. Programs built with Stabilizer run with randomly-placed functions, stack frames, and heap objects. Functions and stack frames are moved repeatedly during execution. A random memory layout eliminates the effect of layout on performance, and repeated randomization leads to normally-distributed execution times. This makes it straightforward to use standard statistical tests for performance evaluation.

A more detailed description of Stabilizer is available in the Paper, which will appear at ASPLOS 2013 in March.


Stabilizer requires LLVM 3.1. Stabilizer runs on OSX and Linux, and supports x86, x86_64, and PowerPC.

Stabilizer requires LLVM 3.1. Follow the directions here to build LLVM 3.1 and the Clang front-end. Stabilizer's build system assumes LLVM include files will be accessible through your default include path.

By default, Stabilizer will use GCC and the Dragonegg plugin to produce LLVM IR. Fortran programs can only be built with the GCC front end. Stabilizer is tested against GCC version 4.6.2.

Stabilizer's compiler driver szc is written in Python. It uses the argparse module, so a relatively modern version of Python (>=2.7) is required.

Building Stabilizer

$ git clone git:// stabilizer
$ make

By default, Stabilizer is build with debug output enabled. Run make clean release to build the release version with asserts and debug output disabled.

Using Stabilizer

Stabilizer includes the szc compiler driver, which builds programs using the Stabilizer compiler transformations. szc passes on common GCC flags, and is compatible with C, C++ and Fortran inputs.

To compile a program in foo.c with Stabilizer, run:

$ szc -Rcode -Rstack -Rheap foo.c -o foo

The -R flags enable randomizations, and may be used in any combination. Stabilizer uses GCC with the Dragonegg plugin as its default front-end. To use clang, pass -frontend=clang to szc.

The resulting executable is linked against with (or .dylib on OSX). Place this library somewhere in your system's dynamic library search path or (preferably) add the Stabilizer base directory to your LD_LIBRARY_PATH or DYLD_LIBRARY_PATH environment variable.


The szchi.cfg and szclo.cfg config files can be installed in a SPEC CPU2006 config directory to build and run benchmarks with Stabilizer. The szchi config -O2 for base and -O3 for peak tuning, and szclo uses -O0 and -O1.

The and scripts were used to drive experiments and collect results. The run script accepts optimization levels, benchmarks to enable (or disable with a "-" prefix), a number of runs, and build configurations in any order. For example:

$ ./ 10 bzip2 code code.stack code.heap.stack

This will run the bzip2 benchmark 10 times in each of three randomization configurations. The runspec tool must be in your path, so cd to your SPEC installation and sourceh shrc first.

$ ./ 10 -astar code link O2 O3

This will run every benchmark except astar 10 times with link randomization at -O2 and -O3 optimization levels.

Be warned: there is no easy way to distinguish O2 and O0 results after the fact: both are marked as "base" tuning. Keep these results in separate directories.

The process script reads .rsf files from SPEC and provides some summary statistics, or collects results in an easy-to-process format.

$ ./ $SPEC/result/*.rsf

This will print average runtimes for each benchmark in each configuration and tuning level for the runs in your SPEC results directory.

Pass the -trim flag to remove the highest and lowest runtimes before computing the average.

The -norm flag tests the results for normality using the Shapiro-Wilk test.

The -all flag dumps all results to console, suitable for pasting into a spreadsheet or CSV file.


Stabilizer is distributed under the GNU GPLv2 license. Contact if you are interested in licensing Stabilizer for commercial use.

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