US 10,310,858 B2 · Controlling transition between using first and second processing circuitry

Abstract

Apparatus and a corresponding method for controlling a transition between use of first processing circuitry and second processing circuitry to execute program instructions are provided. Transition monitoring storage selects an entry for a load program instruction executed during the transition in dependence on a memory address from which a value is to be loaded and stores a program order timestamp for the load program instruction, unless a valid previously stored program order timestamp in the entry precedes the program order timestamp. Thus the oldest timestamp of an load instruction executed in the transition is held. At either the start or end (or both) of the transition the content of the transition monitoring storage is cleared. When a store program instruction is executed during the transition and when a further program order timestamp for the store program instruction indicates that the store program instruction precedes in program order a load program instruction already executed in the transition, program instructions which follow the store program instruction in the first and second processing circuitry are squashed and re-executed. Data hazards which could otherwise arise during the transition are thus avoided by the use of transition monitoring storage which is nevertheless conveniently small.

Claims13

Dependent claims

An apparatus for processing data comprising:

first processing circuitry to execute program instructions;
second processing circuitry to execute program instructions;
control circuitry to control a transition between a first state in which program instructions are executed by the first processing circuitry and a second state in which program instructions are executed by the second processing circuitry;
and
transition monitoring storage to select an entry for a load program instruction executed during the transition in dependence on a memory address from which a value is to be loaded and to store in the entry a program order timestamp for the load program instruction unless a valid previously stored program order timestamp in the entry precedes the program order timestamp, wherein the transition monitoring storage is responsive to a signal from the control circuitry indicating either a start or an end of the transition to clear content of the transition monitoring storage,
and wherein the apparatus is responsive to execution of a store program instruction during the transition, when said entry in the transition monitoring storage is selected for the store program instruction, and when a further program order timestamp for the store program instruction indicates that the store program instruction precedes the load program instruction in program order, to squash and re-execute program instructions which follow the store program instruction in the first and second processing circuitry.

3 more elements

Dependencies are inferred from the claim text.

Controlling transition between using first and second processing circuitry

Life of this patent

Controlling transition between using first and second processing circuitry

Life of this patent

Abstract

Claims13