System and method for facilitating avoidance of an exception of a predetermined type in a digital computer system by providing fix-up code for an instruction in response to detection of an exception condition resulting from execution thereof

摘要

A system for avoiding exceptional conditions during execution of a program comprises an execution environment for executing the program and a fix-up code generation subsystem. The program comprises an instruction stream comprising a series of instructions, and the execution environment includes an exceptional condition detector for detecting at least one predetermined type of exceptional condition in connection with execution of each instruction in the instruction stream. The fix-up code generation subsystem is responsive to detection by the execution environment of an exceptional condition of the predetermined type in connection with execution of an instruction in the instruction stream for generating fix- up code which, when processed, would avoid the exceptional condition of that predetermined type, and substitutes the fix- up code in the instruction stream for the instruction in the instruction stream for which the at least one exceptional condition was detected. As a result, if the instruction which gave rise to the exception is in a loop or the like, instead of the instruction being processed, the fix-up code will be processed, which will avoid the exception condition.