Software Pipelining for Transport-Triggered Architectures

This paper discusses software pipelining for a new class of ar-chitectures that we call transport-triggered. These architectures reduce the interconnection requirements between function units. They also exhibit code scheduling possibilities which are not avail-able in traditional operation-triggered architectures. In addition the scheduling freedom is extended by the use of so-called hybrid-pipelined function utits. In order to exploit this tleedom, existing scheduling techniques need to be extended. We present a software pipelirtirtg tech-nique, based on Lam’s algorithm, which exploits the potential of!mnsport-triggered architectures. Performance results are presented for several benchmak loops. Depending on the available transport capacity, MFLOP rates may increase significantly as compared to scheduling without the ex~a degrees of freedom. As stated in [5] transport-triggered MOVE architectures have extra irtstxuction scheduling degrees of tkeedom. This paper investigates if and how those extra degrees influence the software pipelining iteration initiation interval. It therefore adapts the existing algo-rithms for software pipelining as developed by Lam [2]. It is shown that transport-triggering may lead to a significant reduction of the iteration initiation interval and therefore to an increase of the MIPS and/or MFLOPS rate. The remainder of this paper starts with an introduction of the MOVE class of architectures; it clari6es the idea of transport-triggered architectures. Section 3 formulates the software pipelin-ing problem and its algorithmic solution for trrmsport-triggered architectures. Section 4 describes the architecture characteristics and benchmarks used for the measurements. In order to research the influence of the extra scheduling freedom, the algorithm has been applied to the benchmarks under dfierent scheduling disci-plines. The next section (5) compares and analysis the measure-ments. Finally section 6 gives severaf conclusions and indicates further research to be done