This project is my experiment to generate a stripped program with dynamic profiling. Namely, to profile hot code path and strip out code that never uses. This obviously will generate incorrect program, but this idea is that given statistically significant tests, can we generate "correct" program for most cases, and this "correct" program will be significantly smaller than the original always correct one?

This implementation as provided now is a proof-of-concept.

You need to have LLVM installed, and check to see if you have llvm-config in your $PATH.

In this proof-of-concept, I provided a demo program in ./tests called gcd.c. First, go to ./tests

./irgen.sh

This command will generate LLVM intermediate representation, thus, ./tests/gcd.ll file.

Go back to ./ directory, and:

make

This, hopefully will generate ./sdtri binary, with this binary, and ./tests/gcd.ll file, you can generate instrumented source code:

./sdtri c tests/gcd.ll tests/gcd.sdt.bc

This will generate LLVM Bitcode file named ./tests/gcd.sdt.bc, go to ./tests directory again, and:

./compile-conv.sh

This will generate binary ./gcd, and you can run:

./gcd 10 4

This will output the greatest common denominator: gcd 2, also, an instrumented output generated in /tmp/sdt.out, which will be used implicitly later.

Now, we have instrumented output, LLVM intermediate representation, the stripped down program can be generated, go back to ./ directory, and:

./sdtri v tests/gcd.ll tests/gcd.v.bc

This will generate stripped down version of original program, how do we know it is stripped down?

llvm-dis tests/gcd.v.bc -o tests/gcd.v.ll

Comparing the lines of code for tests/gcd.v.ll with tests/gcd.ll, you can see tets/gcd.v.ll has less lines of code.

Now, to compile the stripped down program, go to ./tests directory:

./compile.sh

This will generate ./tests/gcd-v file, which is the stripped down version of the original program. You can see the output:

./gcd-v 10 4

Well, it is still correct. But how about other cases?

./gcd-v 14 35

Again, it outputs 7, which is the same as original gcd program. Pretty good. However, it will break down in case:

./gcd-v 0 12

Oops, now while the original program will gives 0, the stripped down version will stuck in a infinite loop :(