Advanced Micro Devices Corporation

Kai Troester

Neil N Marketkar

Emil Talpes

Krishnan V Ramani

Matthew T Sobel

Paul J Moyer

Douglas Benson Hunt

David N Suggs

Michael David Achenbach

Luke Yen

Ashok Tirupathy Venkatachar

Frank C Galloway

Betty Ann McDaniel

Joshua James Lindner

Marius Evers

Jay E Fleischman

John M King

Michael Estlick

Erik D Swanson

Magiting M Talisayon

Scott Thomas Bingham

Benjamin Floering

Hongwen Gao

Mike Butler

Andrej Kocev

Tim J Wilkens

Michael W Long

Johnny C Chu

Srinivas Keshav

Robert Weidner

Systems, apparatuses, and methods for compressing multiple instruction operations together into a single retire queue entry are disclosed. A processor includes at least a scheduler, a retire queue, one or more execution units, and control logic. When the control logic detects a given instruction operation being dispatched by the scheduler to an execution unit, the control logic determines if the given instruction operation meets one or more conditions for being compressed with one or more other instruction operations into a single retire queue entry. If the one or more conditions are met, two or more instruction operations are stored together in a single retire queue entry. By compressing multiple instruction operations together into an individual retire queue entry, the retire queue is able to be used more efficiently, and the processor can speculatively execute more instructions without the retire queue exhausting its supply of available entries.

Retire queue compression

Systems, apparatuses, and methods for arbitrating threads in a computing system are disclosed. A computing system includes a processor with multiple cores, each capable of simultaneously processing instructions of multiple threads. When a thread throttling unit receives an indication that a shared cache has resource contention, the throttling unit sets a threshold number of cache misses for the cache. If the number of cache misses exceeds this threshold, then the throttling unit notifies a particular upstream computation unit to throttle the processing of instructions for the thread. After a time period elapses, if the cache continues to exceed the threshold, then the throttling unit notifies the upstream computation unit to more restrictively throttle the thread by performing one or more of reducing the selection rate and increasing the time period. Otherwise, the unit notifies the upstream computation unit to less restrictively throttle the thread.

Throttling while managing upstream resources

A processor includes a load/store unit and an execution pipeline to execute an instruction that represents a single-instruction-multiple-data (SIMD) operation, and which references a memory block storing operand data for one or more lanes of a plurality of lanes and a mask vector indicating which lanes of a plurality of lanes are enabled and which are disabled for the operation. The execution pipeline executes an instruction in a first execution mode unless a memory fault is generated during execution of the instruction in the first execution mode. In response to the memory fault, the execution pipeline re-executes the instruction in a second execution mode. In the first execution mode, a single load operation is attempted to access the memory block via the load/store unit. In the second execution mode, a separate load operation is performed by the load/store unit for each enabled lane of the plurality of lanes prior to executing the SIMD operation.

Masked multi-lane instruction memory fault handling using fast and slow execution paths

Systems, apparatuses, and methods for implementing a fastpath microcode sequencer are disclosed. A processor includes at least an instruction decode unit and first and second microcode units. For each received instruction, the instruction decode unit forwards the instruction to the first microcode unit if the instruction satisfies at least a first condition. In one implementation, the first condition is the instruction being classified as a frequently executed instruction. If a received instruction satisfies at least a second condition, the instruction decode unit forwards the received instruction to a second microcode unit. In one implementation, the first microcode unit is a smaller, faster structure than the second microcode unit. In one implementation, the second condition is the instruction being classified as an infrequently executed instruction. In other implementations, the instruction decode unit forwards the instruction to another microcode unit responsive to determining the instruction satisfies one or more other conditions.

Fastpath microcode sequencer

An approach is provided for allocating a shared resource to threads in a multi-threaded microprocessor based upon the usefulness of the shared resource to each of the threads. The usefulness of a shared resource to a thread is determined based upon the number of entries in the shared resource that are allocated to the thread and the number of active entries that the thread has in the shared resource. Threads that are allocated a large number of entries in the shared resource and have a small number of active entries in the shared resource, indicative of a low level of parallelism, can operate efficiently with fewer entries in the shared resource, and have their allocation limit in the shared resource reduced.

Shared resource allocation in a multi-threaded microprocessor

Techniques for use in a microprocessor core for soft watermarking in thread shared resources implemented through thread mediation. A thread is removed from a thread mediation decision involving multiple threads competing or requesting to use a shared resource at a current clock cycle based on a number of entries in the shared resource that the thread is estimated to have allocated to it at the current clock cycle. By removing the thread from the thread mediation decision, the thread is stalled from allocating additional entries in the shared resource.

Soft watermarking in thread shared resources implemented through thread mediation

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

Systems and methods selectively bypass address-generation hardware in processor instruction pipelines. In an embodiment, a processor includes an address-generation stage and an address-generation-bypass-determination unit (ABDU). The ABDU receives a load/store instruction. If an effective address for the load/store instruction is not known at the ABDU, the ABDU routes the load/store instruction via the address-generation stage of the processor. If, however, the effective address of the load/store instruction is known at the ABDU, the ABDU routes the load/store instruction to bypass the address-generation stage of the processor.

Systems and methods for selectively bypassing address-generation hardware in processor instruction pipelines

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.

A processor employs a prediction table at a front end of its instruction pipeline, whereby the prediction table stores address register and offset information for store instructions; and stack offset information for stack access instructions. The stack offset information for a corresponding instruction indicates the location of the data accessed by the instruction at the processor stack relative to a base location. The processor uses pattern matching to identify predicted dependencies between load/store instructions and predicted dependencies between stack access instructions. A scheduler unit of the instruction pipeline uses the predicted dependencies to perform store-to-load forwarding or other operations that increase efficiency and reduce power consumption at the processing system.

Stack access tracking using dedicated table

A processor employs a prediction table at a front end of its instruction pipeline, whereby the prediction table stores address register and offset information for store instructions; and stack offset information for stack access instructions. The stack offset information for a corresponding instruction indicates the entry of the stack accessed by the instruction stack relative to a base entry. The processor uses pattern matching to identify predicted dependencies between load/store instructions and predicted dependencies between stack access instructions. A scheduler unit of the instruction pipeline uses the predicted dependencies to perform store-to-load forwarding or other operations that increase efficiency and reduce power consumption at the processing system.

Stack access tracking

A method and microprocessor are described for efficiently executing load instructions out-of-order (speculatively). The microprocessor includes an enhanced load store unit (LSU) and an enhanced instruction decoder. The enhanced LSU receives a plurality of out-of-order value addresses, and sends a resync signal to the enhanced instruction decoder when an execution error associated with a particular load instruction occurs. The enhanced instruction decoder stores a specific address associated with the particular load instruction, and increments a counter value that indicates how many times the resync signal was sent by the resync predictor. When the counter value reaches a predetermined threshold, subsequent load instructions from the specific address are executed in order (non-speculatively). When a future execution of the particular load instruction indicates that the probability of an execution error has been reduced, the counter value is decremented, facilitating newer load instructions associated with the same address to again be executed speculatively.

Growing community of inventors

Boxborough, MA, United States of America

Kai Troester