In this paper, we present the overall design of the Agassiz compiler [1]. The Agassiz compiler is an integrated compiler targeting the concurrent multithreaded architectures [12,13]. These architectures can exploit both loop-level and instruction-level parallelism for general-purpose applications (such as those in SPEC benchmarks). They also support various kinds of control and data speculation, runtime data dependence checking, and fast synchronization and communication mechanisms. The Agassiz compiler has a loop-level parallelizing compiler as its front-end and an instruction-level optimizing compiler as its back-end to support such architectures. In this paper, we focus on the IR design of the Agassiz compiler and describe how we support the front-end analyses, various optimization techniques, and source-to-source translation.