International Business Machines Corporation

Bryan J Lloyd

Balaram Sinharoy

David Allen Hrusecky

David A Campbell

Dung Q Nguyen

Eric M Foster

Shih-Hsiung Stephen Tung

Christopher J Gonzalez

Kimberly Marie Fernsler

Hung Qui Le

Brian Chen

Chuck Hong Ngai

Brian William Thompto

David Scott Ray

Robert Allen Cordes

Benjamin W Stolt

David Coupe

Samuel David Kirchhoff

Guy L Guthrie

Brian David Barrick

Sundeep Chadha

Susan Elizabeth Eisen

Jeffrey A Stuecheli

Harold Wade Cain, Iii

Sheldon Bernard Levenstein

Mohit Karve

Kenneth Lundy Ward

George W Rohrbaugh, Iii

Vivek Britto

Dennis E Franklin

Derek E Williams

Fadi Y Busaba

Hugh Shen

Phillip G Williams

Christian Zoellin

Kurt Alan Feiste

Richard Eugene Anderson

Dwain Alan Hicks

John Barry Griswell, Jr

Michael Thomas Vaden

Dhivya Jeganathan

Edmund Joseph Gieske

Ronald S Svec

Luke Murray

Michael James Mack

Francesco A Campisano

Jake Truelove

Daniel J Buerkle

Christian Gerhard Zoellin

A computer system, processor, programming instructions and/or method for managing operations of a gather buffer for a processor core load storage unit. The processor core includes a processing pipeline having one or more execution units for processing unaligned load instructions that executes in two phases to satisfy. A buffer storage element is provided having a plurality of entries for temporarily collecting partial writeback results retrieved from the memory that are associated with first phase accesses for each of a plurality of unaligned load instructions. An associated logic controller device tracks two parts of the unaligned load to be gathered at independent times, wherein said partial result stored at said buffer storage element comprises a first part of an unaligned load. The second phase load access for the same instruction is independently accessed and later merged with first part of the load data at byte granularity to satisfy the load.

Gather buffer management for unaligned and gather load operations

A first instruction for processing by a processor core is received. Whether the instruction is a larx is determined. Responsive to determining the instruction is a larx, whether a cacheline associated with the larx is locked is determined. Responsive to determining the cacheline associated with the larx is not locked, the cacheline associated with the larx is locked and a counter associated with a first thread of the processor core is started. The first thread is processing the first instruction.

Prioritization of threads in a simultaneous multithreading processor core

Technology for fusing certain load instructions and compare-immediate instructions in a computer processor having a load-store architecture with respect to transferring data between memory and registers of the computer processor. In some embodiments the load and compare-immediate instructions are consecutive. In some embodiments, the instructions are only merged if: (i) the respective RA and RT fields of the two instructions match; (ii) the immediate field of the compare-immediate instruction has a certain value, or falls within a range of certain values; and/or (iii) the instructions are received in a consecutive manner.

Microprocessor that fuses load and compare instructions

A method for operation of a processor core is provided. A rejected first load instruction is received that has been rejected due to a false load-hit-store detection against a first store instruction. A warning label is generated on a basis of the false load-hit-store detection. The warning label is added to the received first load instruction to create a labeled first load instruction. The labeled first load instruction is issued such that the warning label causes the labeled first load instruction to bypass the first store instruction in the store reorder queue and thereby avoid another false load-hit-store detection against the first store instruction. A computer system and a processor core configured to operate according to the method are also disclosed herein.

Processor overriding of a false load-hit-store detection

A system and method of handling data access demands in a processor virtual cache that includes: determining if a virtual cache data access demand missed because of a difference in the context tag of the data access demand and a corresponding entry in the virtual cache with the same virtual address as the data access demand; in response to the virtual cache missing, determining whether the alias tag valid bit is set in the corresponding entry of the virtual cache; in response to the alias tag valid bit not being set, determining whether the virtual cache data access demand is a synonym of the corresponding entry in the virtual cache; and in response to the virtual access demand being a synonym of the corresponding entry in the virtual cache with the same virtual address but a different context tag, updating information in a tagged entry in an alias table.

Virtual cache synonym detection using alias tags

A computer system includes a processor and a prefetch engine. The processor is configured to generate a demand access stream. The prefetch engine is configured to generate a first prefetch request and a second prefetch request based on the demand access stream, to output the first prefetch request to a first translation lookaside buffer (TLB), and to output the second prefetch request to a second TLB that is different from the first TLB. The processor performs a first TLB lookup in the first TLB based on one of the demand access stream or the first prefetch request, and performs a second TLB lookup in the second TLB based on the second prefetch request.

Translation bandwidth optimized prefetching strategy through multiple translation lookaside buffers

A method for operation of a processor core is provided. First instruction data is consulted to determine whether a second instruction has execution data that matches the first instruction data. The first instruction data is from a first instruction. In response to determining that the second instruction has execution data that matches the first instruction data, prior data is copied into the second instruction. The first instruction depends on the prior data. After receiving an availability indication of the prior data, both the first instruction and the second instruction are woken for execution, without requiring execution of the first instruction before waking of the second instruction. The second instruction is executed by using the prior data as a skip of the first instruction. A computer system and a processor core configured to operate according to the method are also disclosed herein.

Execution elision of intermediate instruction by processor

A memory-referent instruction is executed to calculate a target effective address (EA) of a corresponding memory-referent request. An array entry in an upper level cache is allocated, and the EA is specified in a corresponding EA directory entry. While in-flight, the memory-referent request is buffered in a queue in association with a pointer to the entry in the EA directory. Based on receiving a translation invalidation request requesting invalidation of an address translation in a translation structure, the processor core walks the EA directory, determines the EA in the entry matches an address range specified by the translation invalidation request, and, based on the match, precisely marks the memory-referent request using the pointer to the EA directory entry. Based on the marking, the translation invalidation request is permitted to complete with reference to the processor core only after the memory-referent request has drained from the processing unit.

Marking in-flight requests affected by translation entry invalidation in a data processing system

In at least one embodiment, a processing unit includes a processor core and a vertical cache hierarchy including at least a store-through upper-level cache and a store-in lower-level cache. The upper-level cache includes a data array and an effective address (EA) directory. The processor core includes an execution unit, an address translation unit, and a prefetch unit configured to initiate allocation of a directory entry in the EA directory for a store target EA without prefetching a cache line of data into the corresponding data entry in the data array. The processor core caches in the directory entry an EA-to-RA address translation information for the store target EA, such that a subsequent demand store access that hits in the directory entry can avoid a performance penalty associated with address translation by the translation unit.

Prefetch store preallocation in an effective address-based cache directory

A load-store unit (LSU) of a processor core determines whether or not a second store operation specifies an adjacent update to that specified by a first store operation. The LSU additionally determines whether the total store data length of the first and second store operations exceeds a maximum size. Based on determining the second store operation specifies an adjacent update and the total store data length does not exceed the maximum size, the LSU merges the first and second store operations and writes merged store data into a same write block of a cache. Based on determining that the total store data length exceeds the maximum size, the LSU splits the second store operation into first and second portions, merges the first portion with the first store operation, and writes store data of the partially merged store operation into the write block.

Writing store data of multiple store operations into a cache line in a single cycle

A system and method of handling access demands in a virtual cache comprising, by a processing system, checking if a virtual cache access demand missed because of a synonym tagged in the virtual cache; in response to the virtual cache access demand missing because of a synonym tagged in the virtual cache, updating the virtual address tag in the virtual cache to a new virtual address tag; searching for additional synonyms tagged in the virtual cache; and in response to finding additional synonyms tagged in the virtual cache, updating the virtual address tag of the additional synonyms to the new virtual address tag.

Virtual cache tag renaming for synonym handling

System includes at least one computer processor having a load store execution unit (LSU) for processing load and store instructions, wherein the LSU includes (a) a store queue having a plurality of entries for storing data, each store queue entry having a data field for storing the data, the data field having a width for storing the data; and (b) a gather buffer for holding data, wherein the processor is configured to: process oversize data larger than the width of the data field of the store queue, and process an oversize load instruction for oversize data by executing two passes through the LSU, a first pass through the LSU configured to store a first portion of the oversize data in the gather buffer and a second pass through the LSU configured to merge the first portion of the oversize data with a second portion of the oversize data.

Handling oversize store to load forwarding in a processor

A computer system, processor, and/or load-store unit has a data cache for storing data, the data cache having a plurality of entries to store the data, each data cache entry addressed by a row and a Way, each data cache row having a plurality of the data cache Ways; a first Address Directory organized and arranged the same as the data cache where each first Address Directory entry is addressed by a row and a Way where each row has a plurality of Ways; a store reorder queue for tracking the store instructions; and a load reorder queue for tracking load instruction. Each of the load and store reorder queues having a Way bit field, preferably less than six bits, for identifying the data cache Way and/or a first Address Directory Way where the Way bit field acts as a proxy for a larger address, e.g. a real page number.

Tracking load and store instructions and addresses in an out-of-order processor

Growing community of inventors

Vestal, NY, United States of America

Bryan J Lloyd