Homework 5

Download, build, and install an LLVM and Clang from their Subversion, as in Homework 1. Be sure to do a Release build and also enable assertions. For example, here is the cmake invocation that I use:

cmake -G Ninja -DLLVM_TARGETS_TO_BUILD=host -DCMAKE_INSTALL_PREFIX=${HOME}/llvm-install -DLLVM_ENABLE_ASSERTIONS=1 -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Release ..

Run "make check-all" (or "ninja check-all" if you decide to use the Ninja build tool) and note the results. Hopefully there won't be any unexpected failures.

Improve the precision of one (or more, if you like) transfer function in llvm/lib/IR/ConstantRange.cpp.

Build and install your modified compiler. Be sure to install it somewhere different than the original one! You'll need to run both compilers. Make sure the output of "make check-all" is unchanged from how it looked before you started hacking on the compiler.

Now, build LLVM two more times, once using the first (unmodified) compiler that you built, once using your hacked compiler. Make sure the output of "make check-all" is as expected, for both compilers.

What to hand in:

- a diff (created using the "diff" utility) of your changes to ConstantRange.cpp

- the difference in text segment size (measured using the "size" utility) of the clang binary for a clang compiled by the first (unmodified) compiler that you compiled and also the hacked one

Please let me know if anything here is unclear!

Here's an example of the output of "ninja check-all" that I get. Depending on your machine, you may get different results. That isn't important. What is important is that whatever output you get isn't changed by your compiler modifications.

regehr@hawking:~/llvm/build$ ninja check-all
[445/445] Running all regression tests
lit.py: /home/regehr/llvm/tools/clang/test/lit.cfg:195: note: using clang: '/home/regehr/llvm/build/./bin/clang'
-- Testing: 30589 tests, 12 threads --
Testing Time: 135.43s
Expected Passes : 22894
Expected Failures : 76
Unsupported Tests : 7619
regehr@hawking:~/llvm/build$