Abstract: Processors and methods related to tracking exact convergence to guide the recovery process in response to a mispredicted branch are provided. An example processor includes a pipeline having a frontend and a backend. The processor further includes a state table for maintaining information related to at least a subset of branches corresponding to instructions being processed by the processor. The processor further includes state logic configured to access the state table and track locations of any exact convergence points associated with branches corresponding to the instructions being processed by the processor. The state logic is further configured to identify a first recovery method for recovering from a misprediction associated with a branch if a location of an exact convergence point associated with the branch is determined to be in the frontend of the pipeline, else identify a second recovery method for recovering from the misprediction associated with the branch.

Abstract: Restoring speculative history used for making speculative predictions for instructions processed in a processor. The processor can be configured to speculatively predict an outcome of a condition or predicate of a conditional control instruction before its condition is fully evaluated in execution. Predictions are made by the processor based on a history that is updated based on outcomes of past predictions. If a conditional control instruction is mispredicted in execution, the processor can perform a misprediction recovery by stalling the instruction pipeline, flushing younger instructions in the instruction pipeline back to the mispredicted conditional control instruction, and then re-fetching instructions in the correct instruction flow path for execution.

Abstract: Systems and methods for reusing load instructions by a processor without accessing a data cache include a load store execution unit (LSU) of the processor, the LSU being configured to determine if a prior execution of a first load instruction loaded data from a first cache line of the data cache and determine if a current execution of the second load instruction will load the data from the first cache line of the data cache. Further, the LSU also determines if a reuse of the data from the prior execution of the first load instruction for the current execution of the second load instruction will lead to functional errors. If there are no functional errors, the data from the prior execution of the first load instruction is reused for the current execution of the second load instruction, without accessing the data cache for the current execution of the second load instruction.

Abstract: Processors and methods related to tracking exact convergence to guide the recovery process in response to a mispredicted branch are provided. An example processor includes a pipeline having a frontend and a backend. The processor further includes a state table for maintaining information related to at least a subset of branches corresponding to instructions being processed by the processor. The processor further includes state logic configured to access the state table and track locations of any exact convergence points associated with branches corresponding to the instructions being processed by the processor. The state logic is further configured to identify a first recovery method for recovering from a misprediction associated with a branch if a location of an exact convergence point associated with the branch is determined to be in the frontend of the pipeline, else identify a second recovery method for recovering from the misprediction associated with the branch.

Abstract: Processors and methods related to tracking exact convergence to guide the recovery process in response to a mispredicted branch are provided. An example processor includes a pipeline having a frontend and a backend. The processor further includes a state table for maintaining information related to at least a subset of branches corresponding to instructions being processed by the processor. The processor further includes state logic configured to access the state table and track locations of any exact convergence points associated with branches corresponding to the instructions being processed by the processor. The state logic is further configured to identify a first recovery method for recovering from a misprediction associated with a branch if a location of an exact convergence point associated with the branch is determined to be in the frontend of the pipeline, else identify a second recovery method for recovering from the misprediction associated with the branch.

Abstract: Processors and methods related to tracking exact convergence to guide the recovery process in response to a mispredicted branch are provided. An example processor includes a pipeline having a frontend and a backend. The processor further includes a state table for maintaining information related to at least a subset of branches corresponding to instructions being processed by the processor. The processor further includes state logic configured to access the state table and track locations of any exact convergence points associated with branches corresponding to the instructions being processed by the processor. The state logic is further configured to identify a first recovery method for recovering from a misprediction associated with a branch if a location of an exact convergence point associated with the branch is determined to be in the frontend of the pipeline, else identify a second recovery method for recovering from the misprediction associated with the branch.

Abstract: Operand pool instruction reservation clustering in a scheduler circuit in a processor is disclosed. The scheduler circuit includes a plurality of operand pool reservation circuits each having an assigned number of source operands for an instruction stored that must be ready before the instruction is issued. Instructions having the same number of source operands that are not yet ready for its issuance can be stored in an operand pool reservation circuit having the same assigned number of source operands. In this manner, the number of reservation entries and associated comparator circuits in the clustered scheduler circuit is distributed among the plurality of operand pool reservation circuits to avoid or reduce an increase in the number of scheduling path connections and complexity in each reservation circuit. This can avoid or reduce an increase in scheduling latency for a given number of reservation entries in the clustered scheduler circuit.

Abstract: Predicting load-based control independent (CI), register data independent (DI) (CIRDI) instructions as CI memory data dependent (DD) (CIMDD) instructions for replay in speculative misprediction recovery in a processor. The processor predicts if a source of a load-based CIRDI instruction will be forwarded by a store-based instruction (i.e. “store-forwarded”). If a load-based CIRDI instruction is predicted as store-forwarded, the load-based CIRDI instruction is considered a CIMDD instruction and is replayed in misprediction recovery. If a load-based CIRDI instruction is not predicted as store-forwarded, the processor considers such load-based CIRDI instruction as a pending load-based CIRDI instruction. If this pending load-based CIRDI instruction is determined in execution to be store-forwarded, the instruction pipeline is flushed and the pending load-based CIRDI instruction is also replayed in misprediction recovery.

Abstract: Opportunistic consumer instruction steering based on producer instruction value prediction in a multi-cluster processor is disclosed. A processor provides producer instructions and consumer instructions to a steering circuit that steers the program instructions to clusters of instruction execution circuits. An input value provided to a consumer instruction may be a produced value of a producer instruction, creating a dependency. The steering circuit steers a producer instruction to a first cluster and, in response to receiving the consumer instruction and the predicted value of the producer instruction, provides the predicted value to at least a second cluster and steers the consumer instruction to the second cluster for execution with the predicted value as the input value.

Abstract: Predicting load-based control independent (CI), register data independent (DI) (CIRDI) instructions as CI memory data dependent (DD) (CIMDD) instructions for replay in speculative misprediction recovery in a processor. The processor predicts if a source of a load-based CIRDI instruction will be forwarded by a store-based instruction (i.e. “store-forwarded”). If a load-based CIRDI instruction is predicted as store-forwarded, the load-based CIRDI instruction is considered a CIMDD instruction and is replayed in misprediction recovery. If a load-based CIRDI instruction is not predicted as store-forwarded, the processor considers such load-based CIRDI instruction as a pending load-based CIRDI instruction. If this pending load-based CIRDI instruction is determined in execution to be store-forwarded, the instruction pipeline is flushed and the pending load-based CIRDI instruction is also replayed in misprediction recovery.

Abstract: Restoring speculative history used for making speculative predictions for instructions processed in a processor. The processor can be configured to speculatively predict an outcome of a condition or predicate of a conditional control instruction before its condition is fully evaluated in execution. Predictions are made by the processor based on a history that is updated based on outcomes of past predictions. If a conditional control instruction is mispredicted in execution, the processor can perform a misprediction recovery by stalling the instruction pipeline, flushing younger instructions in the instruction pipeline back to the mispredicted conditional control instruction, and then re-fetching instructions in the correct instruction flow path for execution.

Abstract: Dynamic hammock branch training for branch hammock detection in an instruction stream executing in a processor is disclosed. A branch hammock detection circuit is configured to dynamically detect branch hammocks in an instruction stream during run-time processing of the instruction stream. In response to an identified conditional branch instruction, the branch hammock detection circuit starts a training process for a potential branch hammock predicated by the conditional branch instruction. The branch hammock detection circuit is configured to determine if an identified in-training branch hammock is an actual branch hammock based on setting a potential convergence point as the target address for the conditional branch instruction based on whether the branch is taken or not taken. If an instruction is processed at the set convergence point, this means the set convergence point can be an actual convergence point and the in-training branch hammock can be detected as an actual branch hammock.

Abstract: Opportunistic consumer instruction steering based on producer instruction value prediction in a multi-cluster processor is disclosed. A processor provides producer instructions and consumer instructions to a steering circuit that steers the program instructions to clusters of instruction execution circuits. An input value provided to a consumer instruction may be a produced value of a producer instruction, creating a dependency. The steering circuit steers a producer instruction to a first cluster and, in response to receiving the consumer instruction and the predicted value of the producer instruction, provides the predicted value to at least a second cluster and steers the consumer instruction to the second cluster for execution with the predicted value as the input value.

Abstract: Operand pool instruction reservation clustering in a scheduler circuit in a processor is disclosed. The scheduler circuit includes a plurality of operand pool reservation circuits each having an assigned number of source operands for an instruction stored that must be ready before the instruction is issued. Instructions having the same number of source operands that are not yet ready for its issuance can be stored in an operand pool reservation circuit having the same assigned number of source operands. In this manner, the number of reservation entries and associated comparator circuits in the clustered scheduler circuit is distributed among the plurality of operand pool reservation circuits to avoid or reduce an increase in the number of scheduling path connections and complexity in each reservation circuit. This can avoid or reduce an increase in scheduling latency for a given number of reservation entries in the clustered scheduler circuit.

Abstract: Tracking and communication of direct/indirect source dependencies of producer instructions executed in a processor to source dependent consumer instructions to facilitate processor optimizations. The processor includes instruction processing circuit configured to process and execute fetched instructions in an instruction stream according to a dataflow execution. The instruction processing circuit includes mechanisms to communicate dependencies to dependent, consumer instructions in an instruction pipeline to facilitate processor optimizations, such as replay of consumer instructions. The instruction processing circuit is configured to track producer instructions and consumer instruction dependencies on its producer instructions in the instruction pipeline in a data structure circuit before the instructions are scheduled for execution.

Abstract: Limiting replay of load-based control independent (CI) instructions in speculative misprediction recovery in a processor. In misprediction recovery, load-based CI instructions are designated as load-based CI, data dependent (CIDD) instructions if a load-based CI instruction consumed forwarded-stored data of a store-based instruction. During the misprediction recovery, replayed load-based CIDD instructions will reevaluate an accurate source of memory load the correct data instead of consuming potentially faulty data that may have been forwarded by a store-based instruction that may have only existed in a mispredicted instruction control flow path. Limiting the replay of load-based CI instructions to only determined CIDD load-based instructions can reduce execution delay and power consumption in an instruction pipeline.

Abstract: Deferring cache state updates in a non-speculative cache memory in a processor-based system in response to a speculative data request until the speculative data request becomes non-speculative is disclosed. The updating of at least one cache state in the cache memory resulting from a data request is deferred until the data request becomes non-speculative. Thus, a cache state in the cache memory is not updated for requests resulting from mispredictions. Deferring the updating of a cache state in the cache memory can include deferring the storing of received speculative requested data in the main data array of the cache memory as a result of a cache miss until the data request becomes non-speculative. The received speculative requested data can first be stored in a speculative buffer memory associated with a cache memory, and then stored in the main data array if the data request becomes non-speculative.

Abstract: A register mapping circuit for recovering a register mapping state associated with a flushed instruction by traversing ROB entries from a snapshot of another register mapping state. The register mapping circuit includes a ROB control circuit, a snapshot circuit, and a register rename recovery circuit (RRRC). The ROB control circuit allocates ROB entries to instructions entering a processor pipeline, including a target ROB entry allocated to a target instruction and other ROB entries allocated to other instructions. The snapshot circuit captures snapshots of logical register-to-physical register mapping states in the rename map table in association with a subset of instructions that could be flushed. If the target instruction is flushed, the RRRC restores the rename map table register mapping state corresponding to the target instruction based on a snapshot in a ROB entry allocated to another instruction, and traverses register mapping updates in the intervening ROB entries.

Abstract: A processor element in a processor-based system is configured to fetch one or more instructions associated with a program binary, where the one or more instructions include an instruction having an immediate operand. The processor element is configured to determine if the immediate operand is a reference to a wide immediate operand. In response to determining that the immediate operand is a reference to a wide immediate operand, the processor element is configured to retrieve the wide immediate operand from a common intermediate lookup table (CILT) in the program binary, where the immediate operand indexes the wide immediate operand in the CILT. The processor element is then configured to process the instruction having the immediate operand such that the immediate operand is replaced with the wide immediate operand from the CILT.

Abstract: Dynamic hammock branch training for branch hammock detection in an instruction stream executing in a processor is disclosed. A branch hammock detection circuit is configured to dynamically detect branch hammocks in an instruction stream during run-time processing of the instruction stream. In response to an identified conditional branch instruction, the branch hammock detection circuit starts a training process for a potential branch hammock predicated by the conditional branch instruction. The branch hammock detection circuit is configured to determine if an identified in-training branch hammock is an actual branch hammock based on setting a potential convergence point as the target address for the conditional branch instruction based on whether the branch is taken or not taken. If an instruction is processed at the set convergence point, this means the set convergence point can be an actual convergence point and the in-training branch hammock can be detected as an actual branch hammock.