Advanced Micro Devices Corporation

Arm Limited

Michael David Achenbach

Francesco Spadini

Emil Talpes

Gregory William Smaus

Abhishek Raja

Ganesh Venkataramanan

Matthew Andrew Rafacz

Christopher J Burke

Yasuo Ishii

David N Suggs

Krishnan V Ramani

Kai Troester

Frank C Galloway

Matthew M Crum

Betty Ann McDaniel

Frederick Daniel Weber

Stephan G Meier

Kevin Michael Lepak

Michael Filippo

William Elton Burky

Norbert Juffa

Marius Evers

John M King

Alexander Cole Shulyak

Robert Greg McDonald

Glen Andrew Harris

Chris Abernathy

Kelvin Domnic Goveas

Bipin Prasad Heremagalur Ramaprasad

Nicholas Andrew Plante

Nicholas Andrew Pfister

Zachary Allen Kingsbury

Noah Bamford

Teik Tan

David Gum Lim

Eric Charles Quinnell

Li Ma

Kevin Lepaak

There is provided an apparatus, method and medium. The apparatus comprises processing circuitry to process instructions and a reorder buffer identifying a plurality of entries having state information associated with execution of one or more of the instructions. The apparatus comprises allocation circuitry to allocate entries in the reorder buffer, and to allocate at least one compressed entry corresponding to a plurality of the instructions. The apparatus comprises memory access circuitry responsive to an address associated with a memory access instruction corresponding to access-sensitive memory and the memory access instruction corresponding to the compressed entry, to trigger a reallocation procedure comprising flushing the memory access instruction and triggering reallocation of the memory access instruction without the compression. The allocation circuitry is responsive to a frequency of occurrence of memory access instructions addressing the access-sensitive memory meeting a predetermined condition, to suppress the compression whilst the predetermined condition is met.

Compression of entries in a reorder buffer

Circuitry comprises two or more clusters of execution units, each cluster comprising one or more execution units to execute processing instructions; and scheduler circuitry to maintain one or more queues of processing instructions, the scheduler circuitry comprising picker circuitry to select a queued processing instruction for issue to an execution unit of one of the clusters of execution units for execution; in which: the scheduler circuitry is configured to maintain dependency data associated with each queued processing instruction, the dependency data for a queued processing instruction indicating any source operands which are required to be available for use in execution of that queued processing instruction and to inhibit issue of that queued processing instruction until all of the required source operands for that queued processing instruction are available and is configured to be responsive to an indication to the scheduler circuitry of the availability of the given operand as a source operand for use in execution of queued processing instructions; and the scheduler circuitry is responsive to an indication of availability of one or more last awaited source operands for a given queued processing instruction, to inhibit issue by the scheduler circuitry of the given queued processing instruction to an execution unit in a cluster of execution units other than a cluster of execution units containing an execution unit which generated at least one of those last awaited source operands.

Circuitry and method

There is provided a data processing apparatus comprising decode circuitry responsive to receipt of a block of instructions to generate control signals indicative of each of the block of instructions, and to analyse the block of instructions to detect a potential hazard instruction. The data processing apparatus is provided with decode circuitry to encode information indicative of a clean restart point into the control signals associated with the potential hazard instruction. The data processing apparatus is provided with data processing circuity to perform out-of-order execution of at least some of the block of instructions, and control circuitry responsive to a determination, at execution of the potential hazard instruction, that data values used as operands for the potential hazard instruction have been modified by out-of-order execution of a subsequent instruction, to restart execution from the clean restart point and to flush held data values from the data processing circuitry.

Determining a restart point in out-of-order execution

An arithmetic unit performs store-to-load forwarding based on predicted dependencies between store instructions and load instructions. In some embodiments, the arithmetic unit maintains a table of store instructions that are awaiting movement to a load/store unit of the instruction pipeline. In response to receiving a load instruction that is predicted to be dependent on a store instruction stored at the table, the arithmetic unit causes the data associated with the store instruction to be placed into the physical register targeted by the load instruction. In some embodiments, the arithmetic unit performs the forwarding by mapping the physical register targeted by the load instruction to the physical register where the data associated with the store instruction is located.

Store-to-load forwarding

An apparatus provides an issue queue having a first section and a second section. Each entry in each section stores operation information identifying an operation to be performed. Allocation circuitry allocates each item of received operation information to an entry in the first section or the second section. Selection circuitry selects from the issue queue, during a given selection iteration, an operation from amongst the operations whose required source operands are available. Availability update circuitry updates source operand availability for each entry whose operation information identifies as a source operand a destination operand of the selected operation in the given selection iteration. A deferral mechanism inhibits from selection, during a next selection iteration, any operation associated with an entry in the second section whose source operands are now available due to that operation having as a source operand the destination operand of the selected operation in the given selection iteration.

Apparatus and method for operating an issue queue

A system and method for tracking stores and loads to reduce load latency when forming the same memory address by bypassing a load store unit within an execution unit is disclosed. Store-load pairs which have a strong history of store-to-load forwarding are identified. Once identified, the load is memory renamed to the register stored by the store. The memory dependency predictor may also be used to detect loads that are dependent on a store but cannot be renamed. In such a configuration, the dependence is signaled to the load store unit and the load store unit uses the information to issue the load after the identified store has its physical address.

Tracking stores and loads by bypassing load store units

A system and method for tracking stores and loads to reduce load latency when forming the same memory address by bypassing a load store unit within an execution unit is disclosed. The system and method include storing data in one or more memory dependent architectural register numbers (MdArns), allocating the one or more MdArns to a MEMFILE, writing the allocated one or more MdArns to a map file, wherein the map file contains a MdArn map to enable subsequent access to an entry in the MEMFILE, upon receipt of a load request, checking a base, an index, a displacement and a match/hit via the map file to identify an entry in the MEMFILE and an associated store, and on a hit, providing the entry responsive to the load request from the one or more MdArns.

Techniques for improving execution of a lock instruction are provided herein. A lock instruction and younger instructions are allowed to speculatively retire prior to the store portion of the lock instruction committing its value to memory. These instructions thus do not have to wait for the lock instruction to complete before retiring. In the event that the processor detects a violation of the atomic or fencing properties of the lock instruction prior to committing the value of the lock instruction, the processor rolls back state and executes the lock instruction in a slow mode in which younger instructions are not allowed to retire until the stored value of the lock instruction is committed. Speculative retirement of these instructions results in increased processing speed, as instructions no longer need to wait to retire after execution of a lock instruction.

Speculative retirement of post-lock instructions

The present invention provides a method and apparatus for scheduling based on tags of different types. Some embodiments of the method include broadcasting a first tag to entries in a queue of a scheduler. The first tag is broadcast in response to a first instruction associated with a first entry in the queue being picked for execution. The first tag includes information identifying the first entry and information indicating a type of the first tag. Some embodiments of the method also include marking at least one second entry in the queue is ready to be picked for execution in response to at least one second tag associated with at least one second entry in the queue matching the first tag.

Hybrid tag scheduler to broadcast scheduler entry tags for picked instructions

A method includes suppressing execution of at least one dependent instruction of a load instruction by a processor using stored dependency information responsive to an invalid status of the load instruction. A processor includes an execution unit to execute instructions and a scheduler. The scheduler is to select for execution in the execution unit a load instruction having at least one dependent instruction and suppress execution of the at least one dependent instruction using stored dependency information responsive to an invalid status of the load instruction.

Dependent instruction suppression

A method includes selecting for execution in a processor a load instruction having at least one dependent instruction. Responsive to selecting the load instruction, the at least one dependent instruction is selectively awakened based on a status of a store instruction associated with the load instruction to indicate that the at least one dependent instruction is eligible for execution. A processor includes an instruction pipeline having an execution unit to execute instructions, a scheduler, and a controller. The scheduler selects for execution in the execution unit a load instruction having at least one dependent instruction. The controller, responsive to the scheduler selecting the load instruction, selectively awakens the at least one dependent instruction based on a status of a store instruction associated with the load instruction to indicate that the at least one dependent instruction is eligible for execution by the execution unit.

Dependence-based replay suppression

A method includes suppressing execution of at least one dependent instruction of a first instruction by a processor responsive to an invalid status of an ancestor load instruction associated with the first instruction. A processor includes an instruction pipeline having an execution unit to execute instructions, a load store unit for retrieving data from a memory hierarchy, and a scheduler unit. The scheduler unit selects for execution in the execution unit a first load instruction having at least one dependent instruction linked to the first load instruction for data forwarding from the load store unit and suppresses execution of a second dependent instruction of the first dependent instruction responsive to an invalid status of the first load instruction.

A method includes suppressing execution of an operation portion of a load-operation instruction in a processor responsive to an invalid status of a load portion of load-operation instruction. A processor includes an instruction pipeline including an execution unit operable to execute instructions and a scheduler unit. The scheduler unit includes a scheduler queue and is operable to store a load-operation in the scheduler queue. The load-operation instruction includes a load portion and an operation portion. The scheduler unit schedules the load portion for execution in the execution unit, marks the operation portion in the scheduler queue as eligible for execution responsive to scheduling the load portion, receives an indication of an invalid status of the load portion, and suppresses execution of the operation portion responsive to the indication of the invalid status.

Dependent instruction suppression in a load-operation instruction

A processor core stores information that maps a physical register to an architectural register in response to an instruction modifying the architectural register. The processor recovers a checkpointed state of a set of architectural registers prior to modification of the architectural register by the instruction by modifying a reference mapping of physical registers to the set of architectural registers using the stored information.

Growing community of inventors

Austin, TX, United States of America

Michael David Achenbach