Analysis of Executable Size Reduction by LLVM passes

Analysis of Executable Size Reduction by LLVM passes

I worked in a team as part of Course Project (Compiler Engineering) to analyze the impact of LLVM Passes on code bloat size and compile time on SPEC 2017 CPU Benchmark. We submitted an abstract of our work in EuroLLVM 2018 and got accepted as Technical talk.

Abstract of the talk:

Analysis of Executable Size Reduction by LLVM passes

V. Sinha, P. Kumar, S. Jain, U. Bora, S. Purini, R. Upadrasta


Increase in the number of embedded devices and the demand to run resource intensive programs on these limited memory systems has necessitated the reduction of executable size of programs. LLVM offers an out-of-box -Oz optimization that is specifically targeted for the reduction of generated executable size. However, the formidable increase in the interest of making smaller and smarter devices has compelled programmers to develop more complicated programs for embedded systems.

In this work, we aim to cater to the specific need of compiler driven reduction of executable size for such memory critical devices. We go beyond the traditional series of passes executed by -Oz; we try to break this series into logical groups and study their effect, as well as the effect of their combinations, on size of the executable.

Our preliminary study over SPEC 2017 benchmarks gives an insight into the comparative effect of the groups of passes on executable size. Our work has potential to enable the developer to tailor a custom series of passes so as to obtain the desired executable size. To further aid such a customization, we create a prediction model (based on simple linear regression) that is correctly able to predict the executable size obtained by a combination of groups when given only the sizes obtained by the individual groups.

Update: Due to unavoidable reasons we could not present the talk at EuroLLVM 2018.