Abstract: A processor core having multiple parallel instruction execution slices and coupled to multiple dispatch queues by a dispatch routing network provides flexible and efficient use of internal resources. The dispatch routing network is controlled to dynamically vary the relationship between the slices and instruction streams according to execution requirements for the instruction streams and the availability of resources in the instruction execution slices. The instruction execution slices may be dynamically reconfigured as between single-instruction-multiple-data (SIMD) instruction execution and ordinary instruction execution on a per-instruction basis, permitting the mixture of those instruction types. Instructions having an operand width greater than the width of a single instruction execution slice may be processed by multiple instruction execution slices configured to act in concert for the particular instructions.

Abstract: An execution slice circuit for a processor core has multiple parallel instruction execution slices and provides flexible and efficient use of internal resources. The execution slice circuit includes a master execution slice for receiving instructions of a first instruction stream and a slave execution slice for receiving instructions of a second instruction stream and instructions of the first instruction stream that require an execution width greater than a width of the slices. The execution slice circuit also includes a control logic that detects when a first instruction of the first instruction stream has the greater width and controls the slave execution slice to reserve a first issue cycle for issuing the first instruction in parallel across the master execution slice and the slave execution slice.

Abstract: A method of operation of a processor core execution unit circuit provides efficient use of area and energy by reducing the per-entry storage requirement of a load-store unit issue queue. The execution unit circuit includes a recirculation queue that stores the effective address of the load and store operations and the values to be stored by the store operations. A queue control logic controls the recirculation queue and issue queue so that that after the effective address of a load or store operation has been computed, the effective address of the load operation or the store operation is written to the recirculation queue and the operation is removed from the issue queue, so that address operands and other values that were in the issue queue entry no longer require storage. When a load or store operation is rejected by the cache unit, it is subsequently reissued from the recirculation queue.

Abstract: A processor core having multiple parallel instruction execution slices and coupled to multiple dispatch queues by a dispatch routing network provides flexible and efficient use of internal resources. The configuration of the execution slices is selectable so that capabilities of the processor core can be adjusted according to execution requirements for the instruction streams. Two or more execution slices can be combined as super-slices to handle wider data, wider operands and/or vector operations, according to one or more mode control signal that also serves as a configuration control signal. The mode control signal is also used to partition clusters of the execution slices within the processor core according to whether single-threaded or multi-threaded operation is selected, and additionally according to a number of hardware threads that are active.

Abstract: A method of operating a processor core having multiple parallel instruction execution slices and coupled to multiple dispatch queues by a dispatch routing network provides flexible and efficient use of internal resources. The configuration of the execution slices is selectable so that capabilities of the processor core can be adjusted according to execution requirements for the instruction streams. Two or more execution slices can be combined as super-slices to handle wider data, wider operands and/or vector operations, according to one or more mode control signal that also serves as a configuration control signal. The mode control signal is also used to partition clusters of the execution slices within the processor core according to whether single-threaded or multi-threaded operation is selected, and additionally according to a number of hardware threads that are active.

Abstract: An execution unit circuit for use in a processor core provides efficient use of area and energy by reducing the per-entry storage requirement of a load-store unit issue queue. The execution unit circuit includes a recirculation queue that stores the effective address of the load and store operations and the values to be stored by the store operations. A queue control logic controls the recirculation queue and issue queue so that that after the effective address of a load or store operation has been computed, the effective address of the load operation or the store operation is written to the recirculation queue and the operation is removed from the issue queue, so that address operands and other values that were in the issue queue entry no longer require storage. When a load or store operation is rejected by the cache unit, it is subsequently reissued from the recirculation queue.

Abstract: A method of processing using an execution slice circuit including multiple parallel instruction execution slices provides flexible and efficient use of internal resources. The execution slice circuit includes a master execution slice for receiving instructions of a first instruction stream and a slave execution slice for receiving instructions of a second instruction stream and instructions of the first instruction stream that require an execution width greater than a width of the slices. The method also detects when a first instruction of the first instruction stream has the greater width and controls the slave execution slice to reserve a first issue cycle for issuing the first instruction in parallel across the master execution slice and the slave execution slice.

Abstract: A method of operation of a processor core having multiple parallel instruction execution slices and coupled to multiple dispatch queues coupled by a dispatch routing network provides flexible and efficient use of internal resources. The dispatch routing network is controlled to dynamically vary the relationship between the slices and instruction streams according to execution requirements for the instruction streams and the availability of resources in the instruction execution slices. The instruction execution slices may be dynamically reconfigured as between single-instruction-multiple-data (SIMD) instruction execution and ordinary instruction execution on a per-instruction basis. Instructions having an operand width greater than the width of a single instruction execution slice may be processed by multiple instruction execution slices configured to act in concert for the particular instructions.

Abstract: A method of managing instruction execution for multiple instruction streams using a processor core having multiple parallel instruction execution slices provides instruction processing flexibility. An event is detected indicating that either resource requirement or resource availability for a subsequent instruction of an instruction stream will not be met by the instruction execution slice currently executing the instruction stream. In response to detecting the event, dispatch of at least a portion of the subsequent instruction is made to another instruction execution slice. The event may be a compiler-inserted directive, may be an event detected by logic in the processor core, or may be determined by a thread sequencer. The execution slices may be dynamically reconfigured as between single-instruction-multiple-data (SIMD) instruction execution, ordinary instruction execution, wide instruction execution.

Abstract: A processor core having multiple parallel instruction execution slices and coupled to multiple dispatch queues by a dispatch routing network provides flexible and efficient use of internal resources. The dispatch routing network is controlled to dynamically vary the relationship between the slices and instruction streams according to execution requirements for the instruction streams and the availability of resources in the instruction execution slices. The instruction execution slices may be dynamically reconfigured as between single-instruction-multiple-data (SIMD) instruction execution and ordinary instruction execution on a per-instruction basis, permitting the mixture of those instruction types. Instructions having an operand width greater than the width of a single instruction execution slice may be processed by multiple instruction execution slices configured to act in concert for the particular instructions.

Abstract: Techniques for managing instruction execution for multiple instruction streams using a processor core having multiple parallel instruction execution slices provide flexibility in execution of program instructions by a processor core. An event is detected indicating that either resource requirement or resource availability will not be met by the execution slice currently executing the instruction stream. In response to detecting the event, dispatch of at least a portion of the subsequent instruction is made to another instruction execution slice. The event may be a compiler-inserted directive, may be an event detected by logic in the processor core, or may be determined by a thread sequencer. The instruction execution slices may be dynamically reconfigured as between single-instruction-multiple-data (SIMD) instruction execution, ordinary instruction execution, wide instruction execution.

Abstract: A method, apparatus, and computer program product are disclosed for ensuring processing fairness in simultaneous multi-threading (SMT) microprocessors. A clock cycle priority is assigned to a first thread and to a second thread during a standard selection state that lasts for an expected number of clock cycles by selecting the first thread to be a primary thread and the second thread to be a secondary thread. If a condition exists that requires overriding, an override state is executed by selecting the second thread to be the primary thread and the first thread to be the secondary thread. The override state is forced to be executed for an override period of time which equals the expected number of clock cycles plus a forced number of clock cycles. The forced number of clock cycles is granted to the first thread in response to the first thread again becoming the primary thread.

Abstract: A method of handling program instructions in a microprocessor which reduces delays associated with mispredicted branch instructions, by detecting the occurrence of a stall condition during execution of the program instructions, speculatively executing one or more pending instructions which include at least one branch instruction during the stall condition, and determining the validity of data utilized by the speculative execution. Dispatch logic determines the validity of the data by marking one or more registers of an instruction dispatch unit to indicate which results of the pending instructions are invalid. The speculative execution of instructions can occur across multiple pipeline stages of the microprocessor, and the validity of the data is tracked during their execution in the multiple pipeline stages while monitoring a dependency of the speculatively executed instructions relative to one another during their execution in the multiple pipeline stages.

Abstract: A method and apparatus for steering instructions dynamically, at issue time, so as to maximize the efficiency of use of execution units being shared by multiple threads being processed by an SMT processor. Resource vectors are used at issue time to redirect instructions, from threads being processed simultaneously, to shared resources for which the multiple threads are competing. The existing resource vectors for instructions that are queued for issuance are analyzed and, where appropriate, dynamically recalculated and modified for maximum efficiency.

Abstract: A method is disclosed in a data processing system for ensuring processing fairness in simultaneous multi-threading (SMT) microprocessors that concurrently execute multiple threads during each clock cycle. A clock cycle priority is assigned to a first thread and to a second thread during a standard selection state that lasts for an expected number of clock cycles. The clock cycle priority is assigned according to a standard selection definition during the standard selection state by selecting the first thread to be a primary thread and the second thread to be a secondary thread during the standard selection state. If a condition exists that requires overriding the standard selection definition, an override state is executed during which the standard selection definition is overridden by selecting the second thread to be the primary thread and the first thread to be the secondary thread.

Abstract: Mechanisms to identify and speculatively execute future instructions during a stall condition are provided. In speculative mode, instruction operands may be invalid due to a number of reasons. Dependency and dirty bits are tracked and used to determine which speculative instructions are valid for execution. A modified value register storage and bit vector are used to improve the availability of speculative results that would otherwise be discarded once they leave the execution pipeline because they cannot be written to the architected registers. The modified general purpose registers are used to store speculative results when the corresponding instruction reaches writeback and the modified bit vector tracks the results that have been stored there. Younger speculative instructions that do not bypass directly from older instructions use this modified data when the corresponding bit in the modified bit vector indicates the data has been modified. Otherwise, data from the architected registers is used.

Abstract: The present invention allows a microprocessor to identify and speculatively execute future load instructions during a stall condition. This allows forward progress to be made through the instruction stream during the stall condition which would otherwise cause the microprocessor or thread of execution to be idle. The data for such future load instructions can be prefetched from a distant cache or main memory such that when the load instruction is re-executed (non speculative executed) after the stall condition expires, its data will reside either in the L1 cache, or will be enroute to the processor, resulting in a reduced execution latency. When an extended stall condition is detected, load lookahead prefetch is started allowing speculative execution of instructions that would normally have been stalled.

Abstract: A method of handling program instructions in a microprocessor which reduces delays associated with mispredicted branch instructions, by detecting the occurrence of a stall condition during execution of the program instructions, speculatively executing one or more pending instructions which include at least one branch instruction during the stall condition, and determining the validity of data utilized by the speculative execution. Dispatch logic determines the validity of the data by marking one or more registers of an instruction dispatch unit to indicate which results of the pending instructions are invalid. The speculative execution of instructions can occur across multiple pipeline stages of the microprocessor, and the validity of the data is tracked during their execution in the multiple pipeline stages while monitoring a dependency of the speculatively executed instructions relative to one another during their execution in the multiple pipeline stages.

Abstract: A method and apparatus are provided for dispatch group checkpointing in a microprocessor, including provisions for handling partially completed dispatch groups and instructions which modify system coherent state prior to completion. An instruction checkpoint retry mechanism is implemented to recover from soft errors in logic. The processor is able to dispatch fixed point unit (FXU), load/store unit (LSU), and floating point unit (FPU) or vector multimedia extension (VMX) instructions on the same cycle. Store data is written to a store queue when a store instruction finishes executing. The data is held in the store queue until the store instruction is checkpointed, at which point it can be released to the coherently shared level 2 (L2) cache.

Abstract: A method, apparatus, and computer program product are disclosed in a data processing system for ensuring processing fairness in simultaneous multi-threading (SMT) microprocessors that concurrently execute multiple threads during each clock cycle. A clock cycle priority is assigned to a first thread and to a second thread during a standard selection state that lasts for an expected number of clock cycles. The clock cycle priority is assigned according to a standard selection definition during the standard selection state by selecting the first thread to be a primary thread and the second thread to be a secondary thread during the standard selection state. If a condition exists that requires overriding the standard selection definition, an override state is executed during which the standard selection definition is overridden by selecting the second thread to be the primary thread and the first thread to be the secondary thread.