Browse Prior Art Database

BSP, Action on Loops

IP.com Disclosure Number: IPCOM000107719D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 23K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+4]

Abstract

This article describes a method of improving performance of Branch History Table (BHT) machines by detecting loops and preventing BHT errors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

BSP, Action on Loops

       This article describes a method of improving performance
of Branch History Table (BHT) machines by detecting loops and
preventing BHT errors.

      A factor in BHT errors is the exit from a loop.  A Branch
Stream Processor (BSP) utilizing the prediction of the BHT can easily
detect the loop closing branch, and, depending on the exit mode,
perform any and all of the following so as to reduce the penalty
associated with Branch Wrong Guess (BWG):
     1)   Anticipate the exit and override the BHT prediction
     2)   Prevent the BHT - BWG from overwriting the result in the
BHT, causing a subsequent BWG when the loop is re-en
countered.
     3)   View the loop as a multi-cycle op and proceed down the exit
path resolving subsequent branch and, if possible, create a hedge
path to lessen BWG penalty subsequent to the loop exit.