A worst case timing analysis technique for multiple-issue machines

Abstract

We propose a worst case timing analysis technique for in-order multiple-issue machines. In the proposed technique, timing information for each program construct is represented by a directed acyclic graph (DAG) that shows dependences among instructions in the program construct. From this information, we derive for each pair of instructions the distance bounds between their issue times. Using these distance bounds, we identify the sets of instructions that can be issued at the same time. Deciding such instructions is an essential task in reasoning about the timing behavior of multiple-issue machines. In order to reduce the complexity of analysis, the distance bounds are progressively refined through a hierarchical analysis over the program syntax tree in a bottom-up fashion. Our experimental results show that the proposed technique can predict the worst case execution times for in-order multiple-issue machines as accurately as ones for simpler RISC processors.