Abstract: A processor implementing an improved method for executing load instructions includes execution circuitry, a plurality of registers, and instruction processing circuitry. The instruction processing circuitry fetches a load instruction and a preceding instruction that precedes the load instruction in program order, and in response to detecting the load instruction, translates the load instruction into separately executable prefetch and register operations. The execution circuitry performs at least the prefetch operation out-of-order with respect to the preceding instruction to prefetch data into the processor and subsequently separately executes the register operation to place the data into a register specified by the load instruction. In an embodiment in which the processor is an in-order machine, the register operation is performed in-order with respect to the preceding instruction.

Abstract: A processor having a reduced data hazard penalty includes a register set, at least one execution unit that executes load instructions to transfer data into the register set, and a load queue. The load queue contains at least one entry, and each occupied entry in the load queue stores load data retrieved by an executed load instruction in association with a target address of the executed load instruction. The load queue has associated queue management logic that, in response to execution by the execution unit of a load instruction, determines by reference to the load queue whether a data hazard exists for the load instruction. If so, the queue management logic outputs load data from the load queue to the register set in accordance with the load instruction, thus eliminating the need to flush and re-execute the load instruction.

Abstract: A processor that efficiently obtains target path instructions in the presence of tight program loops includes at least one execution unit for executing instructions and instruction sequencing logic that supplies instructions to the at least one execution unit for execution. The instruction sequencing logic includes an instruction fetch buffer and a branch prediction unit including a branch target cache. In response to prediction of a branch instruction as taken, the branch target cache causes multiple copies of a target instruction group to be loaded into the instruction fetch buffer under the assumption that the branch instruction is a member of the target instruction group. Thereafter, the branch target cache causes all but one of the multiple copies to be canceled from the instruction fetch buffer prior to dispatch if the branch instruction does not belong to the target instruction group.

Abstract: A processor includes a register set, at least one execution unit that executes load instructions to transfer data into the register set, a load queue and associated queue management logic. The load queue contains a plurality of entries that each include a reservation valid field, and each of the plurality of entries is associated with a respective one of a corresponding plurality of load instructions that includes at least one load-reserve instruction. In response to execution of the load-reserve instruction, the queue management logic detects whether a data hazard exists by reference to the load queue, and if so, initiates correction of the data hazard. In addition, the queue management logic records a reservation for the load-reserve instruction by setting the reservation valid field of an entry in the load queue associated with the load-reserve instruction.

Abstract: A processor includes instruction sequencing logic, execution circuitry, data storage coupled to the execution circuitry, and test circuitry. The test circuitry detects for a hardware error in one of the instruction sequencing logic, execution circuitry, and data storage during functional operation of the processor in response to an instruction within an instruction stream provided by the instruction sequencing logic. In one embodiment, a hardware error can be detected by comparing values output in response to a test instruction by redundant circuitry that performs the same function. Alternatively or in addition, a hardware error can be detected by performing an arithmetic or logical operation having a known result (e.g., multiplication by 1, addition of 0, etc.) in response to the test instruction.

Abstract: A data processing system and method of fetching instructions in a data processing system are described. The data processing system includes at least one execution unit that executes fetched instructions and instruction sequencing logic that fetches instructions from memory. In response to detection of a particular instruction trigger within an instruction stream, the instruction sequencing logic fetches one or more non-sequential blocks of instructions from memory, where each of the non-sequential blocks includes a plurality of instructions.