Abstract: An improved method, apparatus, and computer instructions for grouping instructions processed in equal sized sets. A current set of instructions is received in an instruction cache for dispatching. A determination is made as to whether any instructions in the current set of instructions are part of a group including a prior set of instructions received in the instruction cache including using a history data structure, wherein the history data structure contains data regarding instructions in the prior set of instructions. Any instructions are grouped into the group with the instruction in response to a determination that the any instructions are part of the group. Instructions in the group units are dispatched to execution using the history data structure, wherein invalid instruction dispatch groupings are avoided.

Abstract: Techniques are described for dynamically controlling the execution of operations within a multi-operation instruction, such as a very long instruction word (VLIW). A programmable processor fetches and executes a first instruction having an operation mask. Based on the operation mask, the processor selectively executes one or more operations within a second instruction. Individual operations within a multi-operation instruction can be selectively enabled and disabled, which is advantageous in many situations, including event handling and code debugging.

Abstract: Detecting a stall condition associated with processor instructions within one or more threads and generating a no-dispatch condition. The stall condition can be detected by hardware and/or software before and/or during processor instruction execution. The no-dispatch condition can be associated with a number of processing cycles and an instruction from a particular thread. As a result of generating the no-dispatch condition, processor instructions from other threads may be dispatched into the execution slot of an available execution pipeline. After a period of time, the instruction associated with the stall can be fetched and executed.

Abstract: In one embodiment, the invention provides a method for examining information about branch instructions. A method, comprising: examining information about branch instructions that reach a write-back stage of processing within a processor, defining a plurality of streams based on the examining, wherein each stream comprises a sequence of basic blocks in which only a last block in the sequence ends in a branch instruction, the execution of which causes program flow to branch, the remaining basic blocks in the stream each ending in a branch instruction, the execution of which does not cause program flow to branch.

Abstract: The present invention relates to a processing method and apparatus for implementing a systolic-array-like structure. Input data are stored in a depth-configurable register means (DCF) in a predetermined sequence, and are supplied to a processing means (FU) for processing said input data based on control signals generated from instruction data, wherein the depth of the register means (DCF) is controlled in accordance with the instruction data. Thereby, systolic arrays can be mapped onto a programmable processor, e.g. a VLIW processor, without the need for explicitly issuing operations to implement the register moves that constitute the delay lines of the array.

Abstract: Techniques for adding more complex instructions and their attendant multi-cycle execution units with a single instruction multiple data stream (SIMD) very long instruction word (VLIW) processing framework are described. In one aspect, an initiation mechanism also acts as a resynchronization mechanism to read the results of multi-cycle execution. This multi-purpose mechanism operates with a short instruction word (SIW) issue of the multi-cycle instruction, in a sequence processor (SP) alone, with a VLIW, and across all processing elements (PEs) individually or as an array of PEs. A number of advantageous floating point instructions are also described.

Abstract: An instruction buffer of the present invention includes a sequence of instructions arranged in an order determined beforehand, and a buffer including entries arranged in a preselected order for storing the sequence of instructions. Any one of the instructions stored in any one of the entries designated by a low entry number is prior, in order, to another instruction stored in another entry designated by a high entry number.

Abstract: Dynamic reformatting of a dispatch group by selective activation of inactive Start bits of instructions within the dispatch group at the time the instructions are read from the IBUF. The number of instructions in the reformatted dispatch groups can vary from as few as one instruction per group to a maximum number of instructions read from the IBUF per cycle. The reformatted dispatch groupings can be terminated after a single cycle, or they can remain reformatted for as many cycles as desired, depending upon need.

Abstract: The invention relates to a processing system comprising a calculation device comprising at least one calculation unit (13), a storage device and a system for switching between the storage device and the calculation device. In order to reduce the size of the switching system, the storage device comprises several banks of registers (21, 22) for storing words, the switching system comprises at least one switching device (24) associated with each bank of registers and the calculation units exchange a word with a bank of registers by means of the associated switching device.

Abstract: Systems and methods for determining dependencies between processor instructions in multiple phases. In one embodiment, a partial comparison is made between the addresses of a sequence of instructions. Younger instructions having potential dependencies on older instructions are suspended if the partial comparison yields a match. One or more subsequent comparisons are made for suspended instructions based on portions of the addresses referenced by the instructions that were not previously compared. If subsequent comparisons determine that the addresses of the instructions do not match, the suspended instructions are reinstated and execution of the suspended instructions is resumed. In one embodiment, data needed by suspended instructions is speculatively requested in case the instructions are reinstated.

Abstract: Partial bitwise permutation instructions are provided in a microprocessor or microcontroller. Partial bitwise permutations may be specified by one or more of the following: a destination specifier, a previous partial value source, a destination subset specifier, and a control specifier.

Abstract: A more efficient method of handling instructions in a computer processor, by associating resource fields with respective program instructions wherein the resource fields indicate which of the processor hardware resources are required to carry out the program instructions, calculating resource requirements for merging two or more program instructions based on their resource fields, and determining resource availability for simultaneously executing the merged program instructions based on the calculated resource requirements. Resource vectors indicative of the required resource may be encoded into the resource fields, and the resource fields decoded at a later stage to derive the resource vectors. The resource fields can be stored in the instruction cache associated with the respective program instructions. The processor may operate in a simultaneous multithreading mode with different program instructions being part of different hardware threads.

Abstract: An interface for transferring data between a central processing unit (CPU) and a plurality of coprocessors is provided. The interface includes an instruction bus and a data bus. The instruction bus is configured to transfer instructions to the plurality of coprocessors in an instruction transfer order, where particular instructions designate and direct one of the plurality of coprocessors to transfer the data to/from the CPU. The data bus is configured to subsequently transfer the data. Data order signals within the data bus prescribe a data transfer order that differs from the instruction transfer order by prescribing a transfer corresponding to a specific outstanding particular instruction, where the data transfer order is relative to outstanding instructions. The outstanding instructions are those of the particular instructions transferred to the one of the plurality of coprocessors that have not completed a data transfer.

Abstract: Hazard detection is simplified by converting a conditional instruction, operative to perform an operation if a condition is satisfied, into an emissary instruction operative to evaluate the condition and an unconditional base instruction operative to perform the operation. The emissary instruction is executed, while the base instruction is halted. The emissary instruction evaluates the condition and reports the condition evaluation back to the base instruction. Based on the condition evaluation, the base instruction is either launched into the pipeline for execution, or it is discarded (or a NOP, or null instruction, substituted for it). In either case, the dependencies of following instructions may be resolved.

Abstract: A processor includes a return stack circuit used for predicting procedure return addresses for instruction pre-fetching, wherein a return stack controller determines the number of return levels associated with a given return instruction, and pops that number of return addresses from the return stack. Popping multiple return addresses from the return stack permits the processor to pre-fetch the return address of the original calling procedure in a chain of successive procedure calls. In one embodiment, the return stack controller reads the number of return levels from a value embedded in the return instruction. A complementary compiler calculates the return level values for given return instructions and embeds those values in them at compile-time. In another embodiment, the return stack circuit dynamically tracks the number of return levels by counting the procedure calls (branches) in a chain of successive procedure calls.

Abstract: A method for creating precise exceptions including checkpointing an exception causing instruction. The checkpointing results in a current checkpointed state. The current checkpointed state is locked. It is determined if any of a plurality of registers require restoration to the current checkpointed state. One or more of the registers are restored to the current checkpointed state in response to the results of the determining indicating that the one or more registers require the restoring. The execution unit is restarted at the exception handler or the next sequential instruction dependent on whether traps are enabled for the exception.

Abstract: A method and apparatus for utilizing multiple microcode flow synonyms or hardware flow synonyms for an instruction is disclosed. In one embodiment, a microcode synonym is created for execution on two or more execution units of differing types. One microcode synonym may be chosen for execution depending upon the availability status of the execution units. In another embodiment, several microcode synonyms may be chosen for execution. The results of the first microcode synonym to complete execution may be retired. If the results of execution of two microcode synonyms do not match, a fault exception may be raised.

Abstract: A configurable coprocessor interface between a central processing unit (CPU) and a coprocessor is provided. The coprocessor interface has an instruction transfer signal group for transferring different instruction types from the CPU to the coprocessor, sequentially or in parallel, a busy signal group, for allowing the coprocessor to signal the CPU that it cannot receive a transfer of one or more of the different instruction types, and an instruction order signal group for indicating to the coprocessor a relative execution order for multiple instructions that are transferred in parallel. In addition, the coprocessor interface includes separate data transfer signal groups for data being transferred from the CPU to the coprocessor, and for data being transferred from the coprocessor to the CPU, along with a data order signal group for indicating a relative order of data (if transferred out-of-order).

Abstract: An adaptive arrangement including a command translation/ordering unit arranged to recognize and convert a first predetermined command unrecognizable/unsupported by an external recipient into a second predetermined command recognizable/supported by the external recipient. Such arrangement is further arranged to control a predetermined ordering of the converted second predetermined command with respect to other commands. The command translation/ordering unit may be arranged to control ordering such that all commands handled prior to the first predetermined command are completed prior to completion of the converted second predetermined command. Further, the command translation/ordering unit may be arranged to control ordering such that all commands handled after the first predetermined command are completed after completion of the converted second predetermined command.

Abstract: Event vectors are included in an instruction tracking structure of a processor to collect history for every instruction flowing through the processor. Such an event vector, by its nature, cannot be whole until the vector's corresponding instruction completes. However, some information for the event vector is collected earlier, i.e., as the instruction flows through the processor prior to completion. Upon completion of the instruction, the instruction's event vector is examined. In each case a determination is made from the instruction history contained in the event vector as to whether a particular instruction has or has not caused or encountered an event of interest. Responsive to the determination, and possibly other information, a selection is made between saving event vector information and discarding the information.