Detecting Redundant Operations with LLVM

by Mingxing Zhang for LLVM Compiler Infrastructure

An operation is classified as redundant if it is either 1) unneeded thus can be simply omitted without changing the program's output; or 2) repeated, which means the result of it is the same as a former run. The prevalent existence of these redundancies is a main cause of performance bugs. I intend to detect them by 1) identifying the redundant operations on instruction granularity with LLVM; and then 2) aggregating them into high-level blocks that worth fixing.