Arm Limited

Yasuo Ishii

Muhammad Umar Farooq

Joseph Michael Pusdesris

Michael Brian Schinzler

Alexander Cole Shulyak

Abhishek Raja

James David Dundas

Chris Abernathy

Chang Joo Lee

Houdhaifa Bouzguarrou

Nicholas Andrew Plante

William Elton Burky

Glen Andrew Harris

Dam Sunwoo

Karthik Sundaram

Jason Lee Setter

Thomas Christopher Grocutt

Michael Filippo

Guillaume Bolbenes

Michael David Achenbach

Thibaut Elie Lanois

Matthew Andrew Rafacz

Jaekyu Lee

David Gum Lim

Muhammed Umar Farooq

Milosch Meriac

Frederic Claude Marie Piry

Peter Richard Greenhalgh

Ian Michael Caulfield

Albin Pierrick Tonnerre

Alastair David Reid

Matthias Lothar Boettcher

Sergio Schuler

Bipin Prasad Heremagalur Ramaprasad

Adrian Montero

Balaji Vijayan

Krishnendra Nathella

Dominic Phillip Mulligan

Jatin Bhartia

Zachary Allen Kingsbury

Jungsoo Kim

Nathan Yong Seng Chong

Eric Charles Quinnell

Steven Daniel Maclean

Anoop Ramachandra Iyer

Sumanth Chengad Raghu

Nicholas Todd Humphries

Joshua David Knebel

Li Ma

Julia Kay Lanier

Nathan Young Seng Chong

A data processing apparatus is provided. Decode circuitry decodes a stream of instructions including a store instruction and a load instruction. Prediction circuitry predicts that the load instruction loads data from memory that is stored to the memory by the store instruction and the prediction is based on a hash of a program counter value of the store instruction.

Store to load forwarding using hashes

A data processing apparatus is provided. Cache circuitry caches data, the data being indexed according to execution contexts of processing circuitry. Receive circuitry receives invalidation requests each referencing a specific execution context in the execution contexts. Invalidation circuitry invalidates at least some of the data in the cache circuitry and filter circuitry filters the invalidation requests based on at least one condition and, when the condition is met, causes the invalidation circuitry to invalidate the data in the cache circuitry.

Filtering invalidation requests

In register renaming circuitry architectural registers specified in instructions are mapped to physical registers using a mapping table. Operations to be performed with respect to the physical registers are generated in dependence on the instructions and on the mapping table entries. When the mapping table has a mapping of a first instruction destination physical register for a first instruction destination architectural register specified in a first instruction, a second instruction specifying the first instruction destination architectural register as a second instruction source architectural register causes an adapted second operation to be generated corresponding to the second instruction using at least one first instruction source physical register as at least one second instruction source physical register. The adapted second operation incorporates a first operation corresponding to the first instruction.

Register rename stage fusing of instructions

An apparatus is provided for limiting the effective utilisation of an instruction fetch queue. The instruction fetch entries are used to control the prefetching of instructions from memory, such that those instructions are stored in an instruction cache prior to being required by execution circuitry while executing a program. By limiting the effective utilisation of the instruction fetch queue, fewer instructions will be prefetched and fewer instructions will be allocated to the instruction cache, thus causing fewer evictions from the instruction cache. In the event that the instruction fetch entries are for instructions that are unnecessary to the program, the pollution of the instruction cache with these unnecessary instructions can be mitigated.

Instruction prefetch throttling

A data processing apparatus is provided that includes storage circuitry. Communication circuitry responds to an access request comprising a requested index with an access response comprising requested data. Coding circuitry performs a coding operation using a current key to: translate the requested index to an encoded index of the storage circuitry at which the requested data is stored or to translate encoded data stored at the requested index of the storage circuitry to the requested data. The current key is based on an execution environment. Update circuitry performs an update, in response to the current key being changed, of: the encoded index of the storage circuitry at which the requested data is stored or the encoded data.

Updating keys used for encryption of storage circuitry

Processing circuitry to execute load operations, each associated with an identifier. Prediction circuitry to receive a given load value associated with a given identifier, and to make, in dependence on the given load value, a prediction indicating a predicted load value for a subsequent load operation to be executed by the processing circuitry and an ID-delta value indicating a difference between the given identifier and an identifier of the subsequent load operation. The predicted load value being predicted in dependence on at least one occurrence of each of the given load value and the predicted load value during execution of a previously-executed sequence of load operations. The prediction circuitry is configured to determine the ID-delta value in dependence on a difference between identifiers associated with the at least one occurrence of each of the given load value and the predicted load value in the previously-executed sequence of load operations.

Predicting a load value for a subsequent load operation

There is provided a data processing apparatus in which decode circuitry receives a memory copy instruction containing an indication of a source area of memory, an indication of a destination area of memory, and an indication of a remaining copy length. In response to receiving the memory copy instruction, the decode circuitry generates at least one active memory copy operation or a null memory copy operation. The active memory copy operation causes one or more execution units to perform a memory copy from part of the source area of memory to part of the destination area of memory and the null memory copy operation leaves the destination area of memory unmodified.

Memcpy micro-operation reduction

An apparatus is provided having pointer storage to store pointer values for a plurality of pointers, with the pointer values of the pointers being differentially incremented in response to a series of increment events. Tracker circuitry maintains a plurality of tracker entries, each tracker entry identifying a control flow instruction and a current active pointer (from amongst the pointers) to be associated with that control flow instruction. Cache circuitry maintains a plurality of cache entries, each cache entry storing a resolved behaviour of an instance of a control flow instruction identified by a tracker entry along with an associated tag value generated when the resolved behaviour was allocated into that cache entry. For a given entry the associated tag value may be generated in dependence on an address indication of the control flow instruction whose resolved behaviour is being stored in that entry and the current active pointer associated with that control flow instruction. Prediction circuitry is responsive to a prediction trigger associated with a replay of a given instance of a given control flow instruction identified by a tracker entry, to cause a lookup operation to be performed by the cache circuitry using a comparison tag value generated in dependence on the address indication of the given control flow instruction and the current active pointer. In the event of a hit being detected in a given cache entry, the resolved behaviour stored in the given cache entry is used as the predicted behaviour of the given instance of the given control flow instruction, provided a prediction confidence metric is met.

Technique for predicting behaviour of control flow instructions

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

A data processing apparatus includes control flow prediction circuitry that generates a control flow prediction in respect of a group of one or more instructions. Storage circuitry used by the control flow prediction circuitry stores data in association with groups of instructions used to generate the control flow prediction for each of the groups of instructions. Control flow prediction update circuitry inserts new data into the storage circuitry in association with a new group of one or more instructions in dependence on one or more conditions being met when a miss occurs for the group of one or more instructions in the storage circuitry.

Selective control flow predictor insertion

A data processing apparatus is provided that comprises rename circuitry for performing a register rename stage of a pipeline in respect of a stream of operations. Move elimination circuitry performs a move elimination operation on the stream of operations in which a move operation is eliminated and the register rename stage performs an adjustment of an identity of registers in the stream of operations to compensate for the move operation being eliminated and demotion circuitry reverses or inhibits the adjustment in response to one or more conditions being met.

Move elimination

A data processing apparatus includes detection circuitry that detects a parent instruction and a child instruction from a stream of instructions. The parent instruction references a destination register that is referenced as a source register by the child instruction. Adjustment circuitry then adjusts the child instruction to produce an adjusted child instruction whose behaviour is logically equivalent to a behaviour of executing the parent instruction followed by the child instruction.

Instruction fusion

There is provided a data processing apparatus in which receive circuitry receives a result signal from a lower level cache and a higher level cache in respect of a first instruction block. The lower level cache and the higher level cache are arranged hierarchically and transmit circuitry transmits, to the higher level cache, a query for the result signal. In response to the result signal originating from the higher level cache containing requested data, the transmit circuitry transmits a further query to the higher level cache for a subsequent instruction block at an earlier time than the further query is transmitted to the higher level cache when the result signal containing the requested data originates from the lower level cache.

Early cache querying

There is provided a data processing apparatus comprising history storage circuitry that stores sets of behaviours of helper instructions for a control flow instruction. Pointer storage circuitry stores pointers, each associated with one of the sets. The behaviours in the one of the sets are indexed according to one of the pointers associated with that one of the sets. Increment circuitry increments at least some of the pointers in response to an increment event and prediction circuitry determines a predicted behaviour of the control flow instruction using one of the sets of behaviours.

Control flow prediction using pointers

There is provided an apparatus, method and medium. The apparatus comprises a store buffer to store a plurality of store requests, where each of the plurality of store requests identifies a storage address and a data item to be transferred to storage beginning at the storage address, where the data item comprises a predetermined number of bytes. The apparatus is responsive to a memory access instruction indicating a store operation specifying storage of N data items, to determine an address allocation order of N consecutive store requests based on a copy direction hint indicative of whether the memory access instruction is one of a sequence of memory access instructions each identifying one of a sequence of sequentially decreasing addresses, and to allocate the N consecutive store requests to the store buffer in the address allocation order.

Allocation of store requests

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Austin, TX, United States of America

Yasuo Ishii