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A Method for Implementation of Near Distance Forward Branches without Fetch Disruption

IP.com Disclosure Number: IPCOM000233988D
Publication Date: 2014-Jan-06
Document File: 2 page(s) / 79K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method is disclosed for implementing near-distance forward branches by skipping instructions in a fetch unit, without disruption of the fetch sequence.

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A Method for Implementation of Near Distance Forward Branches without Fetch Disruption

Generally, in some code patterns, a few instructions are skipped either conditionally, or unconditionally. Currently, these forward branches are implemented using branch prediction and a branch fetch redirect. After executing a forward branch, all fetched instructions are discarded and fetching starts again, which results in a disruption of

instruction fetch. Further, no branch instructions are currently known that can skip instructions, and are compatibly implemented as either instruction skipping, or as branching across a range of processors. Also, no skipping is known based on the value of a distance field in a branch, and/or a combination of a distance field and a condition.

Disclosed is a method for implementing near-distance forward branches by skipping instructions in a fetch unit, without disruption of the fetch sequence. Firstly, the method determines whether a branch is a near/far forward branch, or a backward branch before executing the branch. A distance field of a branch is determined from

an immediate program counter (PC) relative field or from a predicted target address.

Then, during instruction fetch, a redirect is suppressed in response to determination of a near-distance branch. Thereafter, either during input buffer (i.e. IBUF) insertion, or group formation, when a near distance branch is identified, a number of instructions is skipped based on the target ad...