How to generate llvm bitcode for large programs with many source code files and a huge Makefile (e.g. memcached)?

Question

I have my pass that I tested on toy programs and now I want to run it on large programs, many of which are open source programs like memcached. Such programs have their own Makefile and a complicated compilation procedure. I want to generate a bitcode file for such programs to let my pass work on them. Help and suggestions will be appreciated!

Answer 1

Depending on what you're pass is doing you can:

• Build with LTO: adding -flto to the CFLAGS and building your application with your own built linker plugin is quite seamless from a build system point of view. However it requires some understand about how to setup LTO.
• Build with your own built clang: adding statically your pass to the LLVM pipeline and use your own built clang. Depending on the build system, exporting CC/CXX environment variable pointing to your installed clang should be enough.
• Build by loading your pass dynamically into clang, for example this is what Polly is (optionally) doing.

Answer 2

If you add -emit-llvm to your clang flags, it will emit BC files instead of object files or LL files instead of assembly.

You'll likely have to modify the makefile some more bit that should get you started in the right direction.