Region Scheduling: An Approach for Detecting and Redistributing Parallelism

Absfruct-In dekeloping compi ler techniques f o r p rog rams targeted f o r paral le l execution, i t is imperat ive that a p rog ram representation be ut i l ized that no t onl? facil i tates the detection a n d scheduling o f parallelism bu t also easil? enables p rog ram transformat ions that increase opportuni t ies f o r parallelism. These requirements are the d r i v i n g force behind region scheduling, a technique applicable t o b o t h tine g ra in a n d coarse g r a i n parallelism. Th is technique eniplo! s a p rog ram representat ion that divide% a p rog ram in to regions eonsi\t ing o f source a n d intermediate level statements a n d enables the expression o f b o t h data a n d con t ro l dependencies. Gu ided b j estimates o f the paral le l ism present in regions, the region scheduler redistr ibutec code, thus p rov id ing opportuni t ie$ for paral le l ism in those regions containing insufficient paral le l ism compared t o the capabil it ies o f the e w c u t i n g architecture. The p rog ram representation a n d the transformat ions are applicable t o bo th structured a n d unstructured programs, niahing region whedu l i ng i iseful fur a wide range o f application\. T h e results o f esperiment5 conducted using the technique in the generation o f code fur a reconfigurable long instruct ion w o r d archi tecture are presented. The adbantageh o f region scheduling over trace scheduling, another technique f o r t rans fo rm ing and detecting tine g r a i n paral le l ism i n progranis. are discussed.