CHANGE IN INSTRUCTION BEHAVIOR WITHIN CODE BLOCK BASED ON PROGRAM ACTION EXTERNAL THERETO

摘要

Extended, alternate and/or modified instruction behavior can be established using a program construct that appears outside a bounded block of program code in such a way that the behavioral changes are limited to the bounded block and coincide with a particular point in the execution thereof. These extensions, alternations and/or modifications are supported in some processor embodiments in ways that add neither additional code space nor additional execution cycles to the bounded block. In general, the particular point in execution of the bounded block may be specified in a variety of ways, including positionally or temporally. Techniques described herein have broad applicability, but will be understood by persons of ordinary skill in the art in the context of certain illustrative code blocks, including zero- (or low-) overhead loops, lightweight procedures and very long instruction word (VLIW) type instruction packets, and processors that support them.