We present a graph coloring register allocator de- signed to minimize the number of dynamic memory references. We cover the program with sets of blocks called tiles and group these tiles into a tree reflecting the program's hierarchical control structure. Registers are allocated for each tile using standard graph coloring techniques and the local allocation and conflict information is passed around the tree in a two phase algorithm. This results in an allocation of reg- isters that is sensitive to local usage patterns while retaining a global perspective. Spill code is placed in less frequently executed portions of the program and the choice of variables to spill is based on usage pat- terns between the spills and the reloads rather than usage patterns over the entire program. 1

This paper describes an experiment undertaken to evaluate the effectiveness of inline substitution as a method of improving the running time of compiled code. Our particular interests are in the interaction between inline substitution and aggressive code optimization. To understand this relationship, we used commercially available FORTRAN optimizing compilers as the basis for our study. This paper reports on the effectiveness of the various compilers at optimizing the inlined code. We examine both the runtime performance of the resulting code and the compile-time performance of the compilers. This work can be viewed as a study of the effectiveness of inlining in modern optimizers; alternatively, it can be viewed as one data point on the overall effectiveness of modern optimizing compilers. We discovered that, with optimizing FORTRAN compilers, (1) object-code growth from inlining is substantially smaller than source-code growth, (2) compile-time growth from inlining is smaller than source-code growth, and (3) the compilers we tested were not able to capitalize consistently inlining

The increasing amount of instruction-level parallelism (ILP) required to fully utilize high issue-rate processors has forced the compiler to perform more aggressive analysis, optimization, parallelization and scheduling on the input programs. Yet, the compiler designer must scale back the use of aggressive transformations in order to contain compile time and memory usage. The root of the problem lies in the function-oriented framework assumed in conventional compilers. Traditionally the compilation process has been built using the function as a compilation unit, because the function provides a convenient partition of the program. However, the size and contents of a function may not provide the best environment for aggressive analysis and optimization. This dissertation presents a technique in which the compiler is allowed to repartition the program into more desirable compilation units, called regions. Placing the compiler in control of the size and contents of the compilation unit reduces the importance of the algorithmic complexity of the applied transformations, allowing more aggressive transformations to be applied while reducing compilation time. The region concept has been traditionally applied within an ILP compiler only in the context of code scheduling. This dissertation proposes extending the concept of region partitioning to

In this paper we look at the register allocation problem. In the literature this problem is frequently reduced to the general graph coloring problem and the solutions to the problem are obtained from graph coloring heuristics. Hence, no algorithm with a good performance guarantee is known. Here we show that when attention is restricted to structured programs which we define to be programs whose control-flow graphs are series-parallel, there is an efficient algorithm that produces a solution which is within a factor of 2 of the optimal solution. We note that even with the above restriction the resulting coloring problem is NP-complete. We also consider how to delete a minimum number of edges from arbitrary controlflow graphs to make them series-parallel and apply our algorithm. We show that this problem is Max SNP hard. However, we define the notion of an approximate articulation point and give efficient algorithms to find approximate articulation points. We present a heuristic for the ...

This paper examines the tradeoffs between these two approaches