Compiling Real-Time Programs with Timing Constraint Refinement and Structural Code Motion

We present a programming language called TCEL (Time-Constrained Event Language), whose semantics is based on time-constrained relationships between observable events. Such a semantics infers only those timing constraints necessary to achieve real-time correctness, without over-constraining the system. Moreover, an optimizing compiler can exploit this looser semantics to help tune the code, so that its worst-case execution time is consistent with its real-time requirements. In this paper we describe such a transformation system, which works in two phases. First the TCEL source code is translated into an intermediate representation. Then an instruction-scheduling algorithm rearranges selected unobservable operations, and synthesizes tasks guaranteed to respect the original event-based constraints. (Also cross-referenced as UMIACS-TR-94-90