Abstract: Apparatus, method and code for fabrication of the apparatus, the apparatus comprising a cache providing a plurality of cache lines, each cache line storing a block of data; cache access control circuitry, responsive to an access request, to determine whether a hit condition is present in the cache; and cache configuration control circuitry to set, in response to a merging trigger event, merge indication state identifying multiple cache lines to be treated as a merged cache line to store multiple blocks of data, wherein when the merge indication state indicates that the given cache line is part of the merged cache line, the cache access control circuitry is responsive to detecting the hit condition to allow access to any of the data blocks stored in the multiple cache lines forming the merged cache line.

Abstract: Apparatus, method and code for fabrication of the apparatus, the apparatus comprising a cache providing a plurality of cache lines, each cache line storing a block of data; cache access control circuitry, responsive to an access request, to determine whether a hit condition is present in the cache; and cache configuration control circuitry to set, in response to a merging trigger event, merge indication state identifying multiple cache lines to be treated as a merged cache line to store multiple blocks of data, wherein when the merge indication state indicates that the given cache line is part of the merged cache line, the cache access control circuitry is responsive to detecting the hit condition to allow access to any of the data blocks stored in the multiple cache lines forming the merged cache line.

Abstract: An apparatus for data processing and a method of data processing are provided. Data processing operations are performed in response to instructions which reference architectural registers using physical registers to store data values when performing the data processing operations. Mappings between the architectural registers and the physical registers are stored, and when a data hazard condition is identified with respect to out-of-order program execution of an instruction, an architectural register specified in the instruction is remapped to an available physical register. A reorder buffer stores an entry for each destination architectural register specified by the instruction, entries being stored in program order, and an entry specifies a destination architectural register and an original physical register to which the destination architectural register was mapped before the architectural register remapped to an available physical register.

Abstract: A data processing system includes an instruction pipeline containing instruction queue circuitry, fusion circuitry and decoder circuitry. The fusion circuitry serves to identify fusible groups of program instructions within a Y-wide window of program instructions and supply a stream of program instructions including such replacement fused program instructions to a X-wide decoder circuitry which decodes X program instructions in parallel using parallel decoders.

Abstract: Apparatuses and methods of data processing are disclosed for processing circuitry having a pipeline of multiple stages. Value prediction storage circuitry holds value predictions, each associated with an instruction identifier. The value prediction storage circuitry performs look-ups and provides the processing circuitry with data value predictions. The processing circuitry speculatively issues a subsequent instruction into the pipeline by provisionally assuming that execution of a primary instruction will result in the generated data value prediction. Allocation of entries into the value prediction storage circuitry is based on a dynamic allocation policy, whereby likelihood of allocation into the value prediction storage circuitry of an data value prediction increases for an executed instruction when the executed instruction is associated with at least one empty processing stage in the pipeline.

Abstract: An apparatus has processing circuitry for executing instructions and fetch circuitry for fetching the instructions for execution. When a branch instruction is encountered by the fetch circuitry, it determines subsequent instructions to be fetched in dependence on an initial branch direction prediction for the branch instruction made by branch prediction circuitry. Value prediction circuitry is used to maintain a predicted result value for one or more instructions, and dispatch circuitry maintains a record of pending instructions that have been fetched by the fetch circuitry and are awaiting execution by the processing circuitry, and selects pending instructions from the record for dispatch to the processing circuitry.

Abstract: A digital processor, method, and a non-transitory computer readable storage medium are described, and include a load pipeline operative to access a data content and convert the data content into a load result. The digital processor also includes a value prediction check circuit that is operative to access a speculative content, determine a predicted value from the speculative content, and determine a masked value by masking the data content with a data mask. The masked value is compared to the predicted value, and an action associated with the load result is commanded based upon the comparing of the masked value and the predicted value.

Abstract: A digital processor, method, and a non-transitory computer readable storage medium are described, and include a load pipeline operative to access a data content and convert the data content into a load result. The digital processor also includes a value prediction check circuit that is operative to access a speculative content, determine a predicted value from the speculative content, and determine a masked value by masking the data content with a data mask. The masked value is compared to the predicted value, and an action associated with the load result is commanded based upon the comparing of the masked value and the predicted value.

Abstract: Apparatus for processing data (2) includes issue circuitry (22) for issuing program instructions (processing operations) to execute either within real time execution circuitry (32) or non real time execution circuitry (24, 26, 28, 30). Registers within a register file (18) are marked as non real time dependent registers if they are allocated to store a data value which is to be written by an uncompleted program instruction issued to the non real time execution circuitry and not yet completed. Issue policy control circuitry (42) responds to a trigger event to enter a real time issue policy mode to control the issue circuitry (22) to issue candidate processing operations (such as program instruction, micro-operations, architecturally triggered processing operations etc.) to one of the non real time execution circuitry or the real time execution circuitry in dependence upon whether that candidate processing operation reads a register marked as a non real time dependent register.

Abstract: An apparatus has processing circuitry for executing instructions and fetch circuitry for fetching the instructions for execution. When a branch instruction is encountered by the fetch circuitry, it determines subsequent instructions to be fetched in dependence on an initial branch direction prediction for the branch instruction made by branch prediction circuitry. Value prediction circuitry is used to maintain a predicted result value for one or more instructions, and dispatch circuitry maintains a record of pending instructions that have been fetched by the fetch circuitry and are awaiting execution by the processing circuitry, and selects pending instructions from the record for dispatch to the processing circuitry.

Abstract: An apparatus and method are provided for using predicted result values. The apparatus has a processing unit that comprises processing circuitry for executing a sequence of instructions, and value prediction circuitry for identifying a predicted result value for at least one instruction. A result producing structure is provided that is responsive to a request issued from the processing unit when the processing circuitry is executing a first instruction, to produce a result value for the first instruction and return that result value to the processing unit. While waiting for the result value from the result producing structure, the processing circuitry can be arranged to speculatively execute at least one dependent instruction using a predicted result value for the first instruction as obtained from the value prediction circuitry.

Abstract: An apparatus and method are provided for using predicted result values. The apparatus has processing circuitry for executing a sequence of instructions, and value prediction storage that comprises a plurality of entries, where each entry is used to identify a predicted result value for an instruction allocated to that entry. Dispatch circuitry maintains a record of pending instructions awaiting execution by the processing circuitry, and selects pending instructions from the record for dispatch to the processing circuitry for execution. The dispatch circuitry is arranged to enable at least one pending instruction to be speculatively executed by the processing circuitry using as a source operand a predicted result value provided by the value prediction storage. Allocation circuitry is arranged to apply a default allocation policy to identify a first instruction to be allocated an entry in the value prediction storage.

Abstract: An apparatus and method are provided for using predicted result values. The apparatus has a processing unit that comprises processing circuitry for executing a sequence of instructions, and value prediction circuitry for identifying a predicted result value for at least one instruction. A result producing structure is provided that is responsive to a request issued from the processing unit when the processing circuitry is executing a first instruction, to produce a result value for the first instruction and return that result value to the processing unit. While waiting for the result value from the result producing structure, the processing circuitry can be arranged to speculatively execute at least one dependent instruction using a predicted result value for the first instruction as obtained from the value prediction circuitry.

Abstract: An apparatus and method are provided for using predicted result values. The apparatus has processing circuitry for executing a sequence of instructions, and value prediction storage that comprises a plurality of entries, where each entry is used to identify a predicted result value for an instruction allocated to that entry. Dispatch circuitry maintains a record of pending instructions awaiting execution by the processing circuitry, and selects pending instructions from the record for dispatch to the processing circuitry for execution. The dispatch circuitry is arranged to enable at least one pending instruction to be speculatively executed by the processing circuitry using as a source operand a predicted result value provided by the value prediction storage. Allocation circuitry is arranged to apply a default allocation policy to identify a first instruction to be allocated an entry in the value prediction storage.

Abstract: A data processing system 2 includes an instruction pipeline 14 containing instruction queue circuitry 28, fusion circuitry 30 and decoder circuitry 32. The fusion circuitry 30 serves to identify fusible groups of program instructions within a Y-wide window of program instructions and supply a stream of program instructions including such replacement fused program instructions to a X-wide decoder circuitry 32 which decodes X program instructions in parallel using parallel decoders 40, 42, 44.

Abstract: Data processing circuitry comprises allocation circuitry to allocate one or more source and destination processor registers, of a set of processor registers each defined by a respective register index, to a processor instruction for use in execution of that processor instruction and to associate, with the processor instruction, information to indicate the register index of the allocated source and destination processor registers; the avocation circuitry being selectively operable to allocate, to a processor instruction, a group of destination processor registers having a subset of their register indices in common and to associate, with the processor instruction, information to indicate the register index of one processor register of the group and identifying information to identify one or more bits of the register index which differ between the processor registers in the allocated group of processor registers.

Abstract: Apparatus for processing data (2) includes issue circuitry (22) for issuing program instructions (processing operations) to execute either within real time execution circuitry (32) or non real time execution circuitry (24, 26, 28, 30). Registers within a register file (18) are marked as non real time dependent registers if they are allocated to store a data value which is to be written by an uncompleted program instruction issued to the non real time execution circuitry and not yet completed. Issue policy control circuitry (42) responds to a trigger event to enter a real time issue policy mode to control the issue circuitry (22) to issue candidate processing operations (such as program instruction, micro-operations, architecturally triggered processing operations etc.) to one of the non real time execution circuitry or the real time execution circuitry in dependence upon whether that candidate processing operation reads a register marked as a non real time dependent register.

Abstract: Data processing circuitry comprises allocation circuitry to allocate one or more source and destination processor registers, of a set of processor registers each defined by a respective register index, to a processor instruction for use in execution of that processor instruction and to associate, with the processor instruction, information to indicate the register index of the allocated source and destination processor registers; the avocation circuitry being selectively operable to allocate, to a processor instruction, a group of destination processor registers having a subset of their register indices in common and to associate, with the processor instruction, information to indicate the register index of one processor register of the group and identifying information to identify one or more bits of the register index which differ between the processor registers in the allocated group of processor registers.

Abstract: An apparatus for data processing and a method of data processing are provided. Data processing operations are performed in response to instructions which reference architectural registers using physical registers to store data values when performing the data processing operations. Mappings between the architectural registers and the physical registers are stored, and when a data hazard condition is identified with respect to out-of-order program execution of an instruction, an architectural register specified in the instruction is remapped to an available physical register. A reorder buffer stores an entry for each destination architectural register specified by the instruction, entries being stored in program order, and an entry specifies a destination architectural register and an original physical register to which the destination architectural register was mapped before the architectural register remapped to an available physical register.

Abstract: An integrated circuit incorporates prefetch circuitry for prefetching program instructions from a memory. The prefetch circuitry includes a branch target address cache. The branch target address cache stores data indicative of branch target addresses of previously encountered branch instructions fetched from the memory. For each previously encountered branch instructions, the branch target address cache stores a tag value indicative of a fetch address of that previously encountered branch instruction. The tag values stored are generated by tag value generating circuitry which performs a hashing function upon a portion of the fetch address such that the tag value has a bit length less than the bit length of the portion of the fetch address concerned.