Fast floating point compare with slower backup for corner cases

US8407275B2 · kind B2 · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Maarten J. Boersma · Holzgerlingen, DE
• Michael K. Kroener · Ehningen, DE
• Silvia M. Mueller · Altdorf, DE
• Jochen Preiss · Eppelheim, DE

Key dates

• Filing date: Oct 22, 2008
• Grant date: Mar 26, 2013
• Expiry date: Jan 25, 2032

Classification

• Technology area (CPC G): Physics
• CPC primary: G06F9/30025
• WIPO field: Computer technology
• WIPO sector: Electrical engineering

Abstract

A floating point processor unit executes a floating point compare instruction with two operands of the same or different precision by comparing the two operands in integer format, which speeds up the execution of the floating point compare instruction significantly. The floating point processor now executes the floating point compare instruction at least twice as fast or faster (e.g., two clock cycles instead of five clock cycles in the prior art) for nearly most operand cases (e.g., 99% of all cases). Only the rare corner cases require additional operations on one of the operands and thus require additional cycles of execution time because the integer compare operation will not work for these corner cases. This is due to the fact that one operand is a single precision subnormal number in an unnormalized representation (i.e., has two representations) and the other operand is in the SP subnormal range such that the integer compare operation will fail.