In this talk I'll discuss the process of porting the Merge function pass to thinlto infrastructure. Funcion merging (FM) is an interprocedural pass useful for code-size optimization. It deduplicates common parts of similar functions and outlines them to a separate function thus reducing the code size. This is particularly useful for code bases making heavy use of templates which gets instantiated in multiple translation units.
Porting FM to thinlto offers leveraging its functionality to dedupe functions across entire program. I'll discuss the engineering effort required to port FM to thinlto. Specifically, functionality to uniquely identify similar functions, augmenting function summary with a hash code, populating module summary index, modifying bitcode reader+writer, and codesize numbers on open source benchmarks.
