Run-time code generation is an alternative and complement to compile-time program analysis and optimization. Static analyses are inherently imprecise because most interesting aspects of run-time behavior are uncomputable. By deferring aspects of compilation to run time, more precise information about program behavior can be exploited, leading to greater opportunities for code improvement. The cost of performing optimization at run time is of paramount importance, since it must be repaid by improved performance in order to obtain an overall speedup. This paper describes a lightweight approach to run-time code generation, called deferred compilation, in which compile-time specialization is employed to reduce the cost of optimizing and generating code at run time. Implementation strategies developed for a prototype compiler are discussed, and the results of preliminary experiments demonstrating significant overall speedup are presented. 1 Introduction Many compiler optimizations depend ...

This paper describes deferred compilation, an alternative and complement to compile-time program analysis and optimization. By deferring aspects of compilation to run time, exact information about programs can be exploited, leading to greater opportunities for code improvement. This is in contrast to the use of static analyses, which are inherently conservative. Deferred compilation automates the translation of ordinary programs into native machine code that performs fast optimization and native-code generation at run time. Automation is obtained through the use of a compile-time staging analysis, which determines the portions of a program that may be safely and profitably compiled at run time. Fast run-time optimization is obtained by trading space for time: compile-time specialization yields numerous run-time code generators, each customized to optimize a small portion of the source program based on run-time information. Implementation strategies developed for a prototype compiler ar...