A link-time optimization (LTO) approach in the EMCA program domain

Abstract: Multi-core systems on chip with a high level of integration are used in high performance network devices and parallel computing systems. Ericsson is using its own multi-core system (EMCA) for various high performance mobile network systems. EMCA, like most embedded multiprocessor systems, is a memory constrained system. Each core has limited amount of local and shared memory for code and data. To achieve high computational density on the system, it is very important to optimize code size to reduce both shared memory access and context switching costs for each computation node. This thesis evaluates the link time optimization (LTO) approach based on a new LLVM back-end for EMCA architecture. Link time optimization (interprocedural optimization) is performed with the entire program code available all at once in link time, or immediately after linking the programs object files. The research carried out during this thesis proves that the LTO approach can be used as a solution for code size reduction in the EMCA program domain. The thesis also evaluates the link time optimization mechanism itself and shows its advantages in general. As for the experimental part, it provides implemen-tation of LTO based on the LLVM framework, compatible with the current programming tool-chain for EMCA.