Abstract: An apparatus comprises processing circuitry 14 to perform data processing in response to instructions, the processing circuitry supporting speculative processing of read operations for reading data from a memory system 20, 22; and control circuitry 12, 14, 20 to identify whether a sequence of instructions to be processed by the processing circuitry includes a speculative side-channel hint instruction indicative of whether there is a risk of information leakage if at least one subsequent read operation is processed speculatively, and to determine whether to trigger a speculative side-channel mitigation measure depending on whether the instructions include the speculative side-channel hint instruction. This can help to reduce the performance impact of measures taken to protect against speculative side-channel attacks.

Abstract: An apparatus includes a processor. The processor includes two memories. The first memory stores one set of instructions. The second memory stores another set of instructions that are longer than the set of instructions in the first memory. An instruction in the set of instructions in the first memory is used as a pointer to a corresponding instruction in the set of instructions in the second memory.

Abstract: A method of operating a processor includes reclaiming a physical register renamed as a microcode architectural register used by a microcode routine. The physical register is reclaimed according to an indicator corresponding to the microcode architectural register and indicating that a pointer to the physical register and corresponding to the microcode architectural register is an active pointer.

Abstract: A method and apparatus are provided for executing instructions from a plurality of instruction threads on a multi-threaded processor. The instruction threads may each include instructions of different complexity. A plurality of pipelines for executing instructions are provided and an instruction scheduler determines on each clock cycle the pipelines upon which instructions will be executed. Some of the pipelines are configured to appear to the instruction threads as single pipelines but in fact include two pipeline paths, one for executed instructions of lower complexity and the other. The instruction scheduler determines on which of the two pipeline paths an instruction should execute.

Abstract: An out-of-order renaming processor is provided with a register file within which aliasing between registers of different sizes may occur. In this way a program instruction having a source register of a double precision size may alias with two single precision registers being used as destinations of one or more preceding program instructions. In order to track this data dependency the double precision register may be remapped into a micro-operation specifying two single precision registers as its source register. In this way, scheduling circuitry may use its existing hazard detection and management mechanisms to handle potential data hazards and dependencies. Not all program instructions having such data hazards between registers of different sizes are handled by this source register remapping. For these other program instructions a slower mechanism for dealing with the data dependency hazard is provided.

Abstract: An out-of-order execution in-order retire microprocessor includes a branch information table comprising N entries. Each of the N entries stores information associated with a branch instruction. The microprocessor also includes a reorder buffer comprising M entries. Each of the M entries stores information associated with an unretired instruction within the microprocessor. Each of the M entries includes a field that indicates whether the unretired instruction is a branch instruction and, if so, a tag identifying one of the N entries in the branch information table storing information associated with the branch instruction. N is significantly less than M such that the overall die space and power consumption is reduced over a processor in which each reorder buffer entry stores the branch information.

Abstract: A processor includes a plurality of executing sections configured to simultaneously execute instructions for a plurality of threads, an instruction issuing section configured to issue instructions to the plurality of executing sections, and an instruction sync monitoring section configured to, when an instruction-synchronizing instruction is issued to one or more of the plurality of executing sections from the instruction issuing section, monitor completion of execution of the instruction-synchronizing instruction for each of the executing sections, to which the instruction-synchronizing instruction has been issued, thus detecting completion of execution of preceding instructions for the thread to which the instruction-synchronizing instruction belongs.

Abstract: A pipeline processor has a first stage to read data from a general purpose register unit, a second stage to execute instruction, and a third stage to write back the data into the general purpose register unit. A pipeline register retains data obtained by executing the second stage. The pipeline register stores a data validity flag. A WRITE suspension unit suspends execution of writing the retained data into a general purpose register of the general purpose register unit until the retained data is rewritten by a subsequent instruction, even if the data validity flag indicates “valid.” A data invalidation unit cancels the execution of writing the data retained in the pipeline register into the general purpose register into which the data is to be written by a preceding instruction and invalidates the retained data, when data is written into the general purpose register by the subsequent instruction.

Abstract: A pipeline operation processor comprises a pipeline processing unit and an instruction insertion controller which inserts an instruction when access to an operation memory is requested, and corrects control information by reference to control information of stages. When a control program is in execution, on receiving an access request instruction requesting for access to the operation memory, the instruction insertion controller inserts an NOP instruction from the instruction decoding unit in place of the access request instruction. The access request instruction is executed while the pipeline processing unit executes no operation, and subsequently, the pipeline processing is continued.