Intel Corporation

Slade A Morgan

Alan Beecher Kyker

Reynold V D'Sa

Stephan Jourdan

Gad Shlomo Sheaffer

Robert F Krick

Gustavo P Espinosa

John Alan Miller

Rebecca E Hebda

Richard A Weier

The present invention provides for a method and apparatus for the detection and prevention of and recovery from bogus branch predictions in a microprocessor. Micro-ops, decoded from a macro instruction, are stored in a decoded micro-op cache. Branch prediction logic determines whether a branch is bogus or not. If the branch taken was determined to be bogus, the present invention causes the micro-ops which descend from the original bogus branch micro-op instruction to be flagged and subsequently moved to the back-end of the processor for retirement. Further, the branch prediction logic (the branch prediction logic storage buffer) is updated as to what the actual direction of the branch was. In this manner then, bogus branches are detected, recovered from and further prevented.

Detection, recovery and prevention of bogus branches

Toggling between accessing an entry in a global history with a stew created from branch predictions implied by the ordering of instructions within a trace of a trace cache when a trace is read out of a trace cache, and accessing an entry in a global history with repeatable variations of a stew when there is more than branch instruction within a trace within the trace cache and at least a second branch instruction is read out.

Method and apparatus for dynamic branch prediction utilizing multiple stew algorithms for indexing a global history

A method and apparatus for predicting the outcome of a branch instruction based on the branch history of preceding branch instruction. As a sequence of instructions passes through an instruction execution pipeline, a base branch instruction is chosen, a history index is generated for the base branch instruction and subsequent branch instructions, and a transform is created for the branch instruction to be predicted. When the sequence of instructions subsequently passes through the pipeline again, the transform is used to operate on the history index of the base branch instruction to produce a history index for the branch to be predicted. The result is used as an index into a prediction array to access the prediction logic for the branch instruction being predicted. By using the predetermined transform, a branch status prediction can be made before the branch to be predicted reaches the normal prediction stage in the pipeline.

Method and apparatus for performing sequential executions of elements in cooperation with a transform

Growing community of inventors

Forest Grove, OR, United States of America

Slade A Morgan