International Business Machines Corporation

John Barry Griswell, Jr

Richard James Eickemeyer

Brian William Thompto

Dung Q Nguyen

Francis Patrick O'Connell

Brian David Barrick

Hung Qui Le

Balaram Sinharoy

Albert Thomas Williams

Jeffrey A Stuecheli

Ehsan Fatehi

William John Starke

Bradly George Frey

Steven J Battle

Cathy May

Mohit Karve

Edward John Silha

Tu-An T Nguyen

Nicholas R Orzol

Eric Jason Fluhr

Mehul N Patel

Ophir Erez

Alper Buyuktosunoglu

Pradip Bose

Philip George Emma

Sundeep Chadha

Bryan J Lloyd

Lee Evan Eisen

Christopher Michael Abernathy

Mary Douglass Brown

Miles Robert Dooley

Todd Alan Venton

Jason Nathaniel Dale

Naga P Gorti

Edmund Joseph Gieske

Zhigang Hu

Donald Ray Stence

Douglas Robert Logan

Richard J Eickemeyer, Jr

A method of performing instructions in a computer processor architecture includes determining that a load instruction is being dispatched. Destination related data of the load instruction is written into a mapper of the architecture. A determination that a compare immediate instruction is being dispatched is made. A determination that a branch conditional instruction is being dispatched is made. The branch conditional instruction is configured to wait until the load instruction produces a result before the branch conditional instruction issues and executes. The branch conditional instruction skips waiting for a finish of the compare immediate instruction.

Dependency skipping in a load-compare-jump sequence of instructions by incorporating compare functionality into the jump instruction and auto-finishing the compare instruction

A system, processor, programming product and/or method including: an instruction dispatch unit configured to dispatch instructions of a compare immediate-conditional branch instruction sequence; and a compare register having at least one entry to hold information in a plurality of fields. Operations include: writing information from a first instruction of the compare immediate-conditional branch instruction sequence into one or more of the plurality of fields in an entry in the compare register; writing an immediate field and the ITAG of a compare immediate instruction into the entry in the compare register; writing, in response to dispatching a conditional branch instruction, an inferred compare result value into the entry in the compare register; comparing a computed compare result value to the inferred compare result value stored in the entry in the compare register; and not execute the compare immediate instruction or the conditional branch instruction.

Inferring future value for speculative branch resolution in a microprocessor

Methods and systems for determining a priority of a threads is described. A processor can execute branch instructions of the thread. The processor can predict branch instruction outcomes of the branch instructions of the thread. The processor can increment a misprediction count of the thread in response to an actual execution of a branch instruction of the thread being different from a corresponding branch instruction prediction outcome of the thread. The processor can determine the priority of the thread based on the misprediction count of the thread.

Thread priorities using misprediction rate and speculative depth

Aspects of the invention include includes determining a first instruction in a processing pipeline, wherein the first instruction includes a compare instruction, determining a second instruction in the processing pipeline, wherein the second instruction includes a conditional branch instruction relying on the compare instruction, determining a predicted result of the compare instruction, and completing the conditional branch instruction using the predicted result prior to executing the compare instruction.

Inferring future value for speculative branch resolution

A computer processor includes a dispatch stage and a dependency skipping execution unit. The dispatch stage is configured to dispatch a plurality of instructions that include a general purpose instruction configured to produce first data, a dependent instruction configured to produce second data, and an indirect dependent instruction configured to produce third data. The dependency skipping execution unit is configured to monitor the plurality of instructions and to process the indirect dependent instruction in response to the general purpose instruction producing the first data. The indirect dependent instruction is issued independently from the second data produced by the indirect dependent instruction.

Dependency skipping execution

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

Processing data in an information handling system is disclosed that includes: in response to an event that triggers a flushing operation, calculate a finish ratio, wherein the finish ratio is a number of finished operations to a number of at least one of the group consisting of in-flight instructions, instructions pending in a processor pipeline, instructions issued to an issue queue, and instructions being processed in a processor execution unit; compare the calculated finish ratio to a threshold; and if the finish ratio is greater than the threshold, then do not perform the flushing operation. Also disclosed is moving the flush point.

Flushing of instructions based upon a finish ratio and/or moving a flush point in a processor

A set of dependence relationships in a set of program instructions is detected by a processor. The set of dependence relationships comprises a first load instruction to load a first data object and a second load instruction to load a second data object from a second address that is provided by address data within the first data object. The processor identifies a number of dependence instances in the set of dependence relationships and determines that the number is over a pattern threshold. The processor sends an enhanced load request to a memory controller. The enhanced load request comprises instructions to load the first data object from a first address on a physical page, locate address data in the first data object based on a memory offset, load the second data object from a second address in the address data, and transmit the first and second data objects to the processor.

Prefetching workloads with dependent pointers

Support for instruction fusion is provided. An indication whether an instruction is a paired instruction is received from an instruction decoder. Based on the indication, one dispatch slot or a paired dispatch slot is allocated in the instruction dispatcher queue. A mapper converts logical addresses of sources and targets of the instruction to physical addresses. Either one issue slot or a paired issue slot is allocated in an issue queue based on the indication from the instruction decoder. The instruction execution environment is loaded into the issue queue and issued to an execution unit.

Pairing issue queues for complex instructions and instruction fusion

Managing application execution by receiving a store instruction, including a store instruction itag and store instruction address, creating a hash of the store instruction address, receiving a load instruction and matching a hash of a store instruction address associated with the load instruction with the hash of the store instruction address associated with the store instruction. The store instruction itag is sent to an instruction sequencing unit (ISU). The ISU delays execution of the load instruction according to the received itag.

Preventing operand store compare conflicts using conflict address data tables

Techniques are disclosed for identifying data streams in a processor that are likely to benefit from data prefetching. A prefetcher receives at least a first request in a plurality of requests to pre-fetch data from a stream in a plurality of streams. The prefetcher assigns a confidence level to the the first request based on an amount of confirmations observed in the stream. The request is in a confident state if the confidence level exceeds a specified value. The first request is in a non-confident state if the confidence level does not exceed the specified value. Doing so allows a memory controller to determine whether to drop the at least the first request based on the confidence level and a memory resource utilization threshold.

Prefetch confidence and phase prediction for improving prefetch performance in bandwidth constrained scenarios

A processor core supporting out-of-order execution (OOE) includes load-hit-store (LHS) hazard prediction at the instruction execution phase, reducing load instruction rejections and queue flushes at the dispatch phase. The instruction dispatch unit (IDU) detects likely LHS hazards by generating entries for pending stores in a LHS detection table. The entries in the table contain an address field (generally the immediate field) of the store instruction and the register number of the store. The IDU compares the address field and register number for each load with entries in the table to determine if a likely LHS hazard exists and if an LHS hazard is detected, the load is dispatched to the issue queue of the load-store unit (LSU) with a tag corresponding to the matching store instruction, causing the LSU to dispatch the load only after the corresponding store has been dispatched for execution.

Processor core including pre-issue load-hit-store (LHS) hazard prediction to reduce rejection of load instructions

A technique for data prefetching for a multi-core chip includes determining memory utilization of the multi-core chip. In response to the memory utilization of the multi-core chip exceeding a first level, data prefetching for the multi-core chip is modified from a first data prefetching arrangement to a second data prefetching arrangement to minimize unused prefetched cache lines. In response to the memory utilization of the multi-core chip not exceeding the first level, the first data prefetching arrangement is maintained. The first and second data prefetching arrangements are different.

Data prefetch ramp implemenation based on memory utilization

A method receives a complex instruction comprising a first portion and a second portion. The method sets a single issue queue slot and allocates an execution unit for the complex instruction, and identifies dependencies in the first and second portions. The method sets a dependency matrix slot and a consumers table slot for the first and section portion. In the event the first portion dependencies have been satisfied, the method issues the first portion and then issues the second portion from the single issue queue slot. In the event the second portion dependencies have not been satisfied, the method places the second portion into a side issue queue. The method issues the second portion when the side issue queue indicates that the second portion is eligible for issue.

System and method for double-issue instructions using a dependency matrix and a side issue queue

A method of prefetching data in a microprocessor includes identifying a data stream associated with a process and determining a depth associated with the data stream based upon prefetch factors including the number of currently concurrent data streams and data consumption rates associated with the concurrent data streams. Data prefetch requests are allocated with the data stream to reflect the determined depth of the data stream. Allocating data prefetch requests may include allocating prefetch requests for a number of cache lines away from the cache line currently being referenced, wherein the number of cache lines is equal to the determined depth. The method may include, responsive to determining the depth associated with a data stream, configuring prefetch hardware to reflect the determined depth for the identified data stream. Prefetch control bits in an instruction executed by the processor control the prefetch hardware configuration.

Growing community of inventors

Austin, TX, United States of America

John Barry Griswell, Jr