LLVM provides many useful command line tools to handle bitcode: opt is the most widely known and is used to run individual passes on an IR module, and llc invokes the backend to generate an assembly or object file from an IR module. Less known but very powerful is bugpoint, the automatic test case reduction tool, that should be part of every developer's toolbox.
The bugpoint tool helps to reduce an input IR file while preserving some interesting behavior, usually a compiler crash or a miscompile. Multiple strategies are involved in the reduction of the test case (shuffling instructions, modifying the control flow, etc.), but because it is oblivious to the LLVM passes and the individual backend specificities, "it may appear to do stupid things or miss obvious simplifications", as stated in the official description. The documentation gives some insights on the strategies that can be involved by bugpoint, but the details are beyond the scope of this post.
Read on to learn how you can use the power of bugpoint to solve some non-obvious problems.
Read on to learn how you can use the power of bugpoint to solve some non-obvious problems.
