The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 27, 2004
Filed:
Oct. 27, 1998
Naresh H. Soni, San Diego, CA (US);
STMicroelectronics, Inc., Carrollton, TX (US);
Abstract
The present invention utilizes a “virtual” condition code (VCC) which can control the instruction sequence in a microprocessor. The virtual condition code is stored in an internal, non-architected register that is not visible to the programmer, but is used by various microprocessor instructions to determine when a branch is to be taken. For example, the virtual condition code can be used as a condition for branching out of a series of repetitive instructions. The virtual condition code (VCC) can eliminate a portion of the processing overhead used when determining whether a sequential number, such as a count value in a register associated with a repetitive instruction, e.g. a LOOP, is zero. In accordance with one aspect of the present invention, a LOOP instruction will decrement a count value in a register (to maintain compatibility with the ISA). However, a corresponding branch instruction will use the virtual condition code, rather than checking the contents of the entire register, to determine whether or not to branch. In this manner, the present invention improves performance by minimizing the amount of hardware resources (i.e. compare logic) utilized while maintaining compatibility with the Intel architecture since the programmer visible condition code is not used. By leaving the programmer visible condition codes unchanged, the software is not forced to save and restore the register contents during each iteration.