Abstract: An apparatus includes a processing pipeline comprising a plurality of stages, the plurality of stages including at least one instruction fusing stage to detect whether a block of instructions to be processed comprises a fusible group of instructions, and to generate a fused instruction to be processed by a subsequent stage of the processing pipeline when said block of instructions comprises said fusible group. However, when said block of instructions comprises a partial subset of said fusible group of instructions, the instruction fusing stage is configured to delay handling of said partial subset of said fusible group of instructions until the instruction fusing stage has determined whether at least one subsequent block of instructions to be processed comprises a remaining subset of instructions of said fusible group.

Abstract: A target apparatus 2 for debug includes a processing pipeline 18 for executing a sequence of program instructions. A debug interface 26 receives debug command signals corresponding directly or indirectly to debug program instructions to be executed. An instruction buffer 24 stores both the debug program instructions and non-debug program instructions. An arbiter 30 selects between both the debug program instructions and the non-debug program instructions stored within the instruction buffer to form the sequence of program instructions to be executed by the processing pipeline. A complex coherent memory system 4, 6, 8, 10, 12, 14, 32 is shared by the debug program instructions and the non-debug program instructions such that they obtain the same coherent view of memory.

Abstract: A data processing apparatus includes a cache memory supporting parallel data loads involving both a first address and a second address. The first address is compared with TAG values stored within a first value store and the second address is compared in parallel with TAG values stored within a second value store. The second value store contains a proper subset of the data value stored within the first value store.

Abstract: A data processing apparatus includes error detection and correction circuitry with an associated hard-error memory buffer. When a correctable hard-error is detected associated with a memory access to a memory, if the hard-error memory buffer is already full, then this correctable hard-error is escalated to be handled as an uncorrectable hard-error. The escalated uncorrectable hard-error is then handled by uncorrectable error handling circuitry (fatal error circuitry) which may trigger an abort of corresponding processing operations by a processor core and force the relinquishing of resources within other circuit elements such as a store buffer.

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.

Abstract: An apparatus includes a processing pipeline comprising a plurality of stages, the plurality of stages including at least one instruction fusing stage to detect whether a block of instructions to be processed comprises a fusible group of instructions, and to generate a fused instruction to be processed by a subsequent stage of the processing pipeline when said block of instructions comprises said fusible group. However, when said block of instructions comprises a partial subset of said fusible group of instructions, the instruction fusing stage is configured to delay handling of said partial subset of said fusible group of instructions until the instruction fusing stage has determined whether at least one subsequent block of instructions to be processed comprises a remaining subset of instructions of said fusible group.

Abstract: A data processing apparatus has at least one memory and processing circuitry. A memory built-in self-test (MBIST) interface receives a MBIST request indicating that a test procedure is to be performed for testing at least one target memory location. Control circuitry detects the MBIST request and reserves for testing at least one reserved memory location including the target memory location. During the test procedure, the memory continues servicing memory transactions issued by the processing circuitry that target a memory location other than the reserved location reserved by the control circuitry. The processing circuitry is stalled if it attempts to access a reserved memory location. Testing consists of short bursts of transactions which occur infrequently. In this way, MBIST testing may continue while the processor is operation in the field with reduced performance impact.

Abstract: A data processing apparatus has at least one memory and processing circuitry. A memory built-in self-test (MBIST) interface receives a MBIST request indicating that a test procedure is to be performed for testing at least one target memory location. Control circuitry detects the MBIST request and reserves for testing at least one reserved memory location including the target memory location. During the test procedure, the memory continues servicing memory transactions issued by the processing circuitry that target a memory location other than the reserved location reserved by the control circuitry. The processing circuitry is stalled if it attempts to access a reserved memory location. Testing consists of short bursts of transactions which occur infrequently. In this way, MBIST testing may continue while the processor is operation in the field with reduced performance impact.

Abstract: A target apparatus 2 for debug includes a processing pipeline 18 for executing a sequence of program instructions. A debug interface 26 receives debug command signals corresponding directly or indirectly to debug program instructions to be executed. An instruction buffer 24 stores both the debug program instructions and non-debug program instructions. An arbiter 30 selects between both the debug program instructions and the non-debug program instructions stored within the instruction buffer to form the sequence of program instructions to be executed by the processing pipeline. A complex coherent memory system 4, 6, 8, 10, 12, 14, 32 is shared by the debug program instructions and the non-debug program instructions such that they obtain the same coherent view of memory.

Abstract: A data processing apparatus 2 includes a cache memory supporting parallel data loads involving both a first address and a second address. The first address is compared with TAG values stored within a first value store 10 and the second address is compared in parallel with TAG values stored within a second value store 14. The second value store 14 contains a proper subset of the data value stored within the first value store 10.

Abstract: A data processing apparatus 2 includes error detection and correction circuitry 8 with an associated hard-error memory buffer 10. When a correctable hard-error is detected associated with a memory access to a memory 6, if the hard-error memory buffer 10 is already full, then this correctable hard-error is escalated to be handled as an uncorrectable hard-error. The escalated uncorrectable hard-error is then handled by uncorrectable error handling circuitry 14 (fatal error circuitry) which may trigger an abort of corresponding processing operations by a processor core 4 and force the relinquishing of resources within other circuit elements such as a store buffer 16.

Abstract: This application is concerned with a device and method for fetching instructions from a data store for processing by a data processor. The device comprises: a register for storing an address of an instruction to be processed by said data processor; a fetch unit responsive to an address input to said fetch unit to fetch an instruction stored at said address; an adder for adding a predetermined amount to said address stored in said register prior to sending said address to said fetch unit, said predetermined amount determining a position in a program flow said fetched instruction has with respect to said instruction addressed in said register; said adder being responsive to detection of a change in program flow to reset said predetermined amount to an initial value, and to increase said predetermined amount for subsequent fetches by an amount equal to the separation between addresses such that consecutive addresses are fetched up to a maximum predetermined amount.

Abstract: An integrated circuit 2 incorporates prefetch circuitry 12 for prefetching program instructions from a memory 6. The prefetch circuitry 12 includes a branch target address cache 28. The branch target address cache 28 stores data indicative of branch target addresses of previously encountered branch instructions fetched from the memory 6. 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 32 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.

Abstract: A data processing system 2 is provided with multiple processors 4, 6 which can operate in either a split-mode in which each processor executes its own program flow or a locked-mode in which the processors execute the same program flow. Debug circuitry 8, 10 is associated with each of the processors. In an emulation-locked mode of operation, one of the processors 4 is active and its respective debug circuitry 8 is active to update the debug state data so as to debug the locked mode code. At the same time, the second processor 6 is held inactive and its state is maintained as well as the debug state data of the debug circuitry 10 within that inactive processor. This maintains the debug state data of the processor 6 across entry and exit to the locked mode of operation.

Abstract: A data processing apparatus is disclosed that comprises a pipelined processor, said pipelined processor comprising a processing pipeline for processing instructions in a plurality of stages, at least some of said plurality of stages each comprising storage elements for storing an instruction or decoded instruction being processed in said stage, said storage elements in at least one of said stages comprising settable elements, each of said settable elements being adapted to store a predetermined value in response to a wake up event, said settable elements being arranged such that in response to said wake up event said values stored in said settable elements form an instruction or decoded instruction.

Abstract: A multiple-processor system 2 is provided where each processor 4-0, 4-1 can be dynamically switched between running in a locked mode where one processor 4-1 checks the operation of the other processor 4-0 and a split mode where each processor 4-0, 4-1 operates independently. Multiple auxiliary circuits 8-0, 8-1 provide auxiliary functions for the plurality of processors 4-0, 4-1. In the split mode, each auxiliary circuit 8-0, 8-1 separately provides auxiliary functions for a corresponding one of the processors 4-0, 4-1. To ensure coherency when each processor 4-0, 4-1 executes a common set of processing operations, in the locked mode a shared one of the auxiliary circuits 8-0 provides auxiliary functions for all of the processors 4-0, 4-1.

Abstract: Interrupt request detection circuitry is disclosed for detecting and outputting interrupt requests to a processor.

Abstract: A multiple-processor system 2 is provided where each processor 4-0, 4-1 can be dynamically switched between running in a locked mode where one processor 4-1 checks the operation of the other processor 4-0 and a split mode where each processor 4-0, 4-1 operates independently. Multiple auxiliary circuits 8-0, 8-1 provide auxiliary functions for the plurality of processors 4-0, 4-1. In the split mode, each auxiliary circuit 8-0, 8-1 separately provides auxiliary functions for a corresponding one of the processors 4-0, 4-1. To ensure coherency when each processor 4-0, 4-1 executes a common set of processing operations, in the locked mode a shared one of the auxiliary circuits 8-0 provides auxiliary functions for all of the processors 4-0, 4-1.

Abstract: A data processing system 2 is provided with multiple processors 4, 6 which can operate in either a split-mode in which each processor executes its own program flow or a locked-mode in which the processors execute the same program flow. Debug circuitry 8, 10 is associated with each of the processors. In an emulation-locked mode of operation, one of the processors 4 is active and its respective debug circuitry 8 is active to update the debug state data so as to debug the locked mode code. At the same time, the second processor 6 is held inactive and its state is maintained as well as the debug state data of the debug circuitry 10 within that inactive processor. This maintains the debug state data of the processor 6 across entry and exit to the locked mode of operation.

Abstract: A processor 4 is provided with reset circuitry 48 which generates a reset signal to reset a plurality of state parameters. Partial reset circuitry 50 is additionally provided to reset a proper subset of this plurality of state parameters. The reset circuitry triggers a redirection of program flow. The partial reset circuitry permits a continuation of program flow. The partial reset circuitry may be used to place processors into a known state with a low latency before switching from a split mode of operation into a locked mode of operation.