634 results about "Instruction stream" patented technology

A microprocessor configured to cache basic blocks of instructions is disclosed. The microprocessor may comprise decoding logic, a basic block cache, and a branch prediction unit. The decoding logic is coupled to receive and decode variable-length instructions into padded instructions that have one of a predetermined number of predetermined lengths. The decoding logic is further configured to form basic blocks of instructions from the padded and decoded instructions. Basic blocks are natural divisions in instruction streams resulting from branch instructions. The start of a basic block is a target of a branch, and the end is another branch instruction. The basic block cache is configured to store the basic blocks in a plurality of storage locations, wherein each storage location is configured to store an address tag, a link bit, and at least a portion of one basic block. The link bit indicates whether the basic block stored in said storage location extends into another storage location. The branch prediction unit has a branch prediction array storing branch prediction information corresponding to each storage location within the basic block cache. A computer system and method for operating are also disclosed.

A fork instruction for execution on a multithreaded microprocessor and occupying a single instruction issue slot is disclosed. The fork instruction, executing in a parent thread, includes a first operand specifying the initial instruction address of a new thread and a second operand. The microprocessor executes the fork instruction by allocating context for the new thread, copying the first operand to a program counter of the new thread context, copying the second operand to a register of the new thread context, and scheduling the new thread for execution. If no new thread context is free for allocation, the microprocessor raises an exception to the fork instruction. The fork instruction is efficient because it does not copy the parent thread general purpose registers to the new thread. The second operand is typically used as a pointer to a data structure in memory containing initial general purpose register set values for the new thread.

A data processing system having a main processor and a coprocessor. The main processor responsds to coprocessor instructions within its instruction stream by issuing the coprocessor instructions upon a coprocessor bus and detecting if the coprocessor accepts them by returning an accept signal. The coprocessor instructions include a coprocessor number and the coprocessor checks this number to see if it matches its own number(s) to determine whether or not it should accept the coprocessor instruction. A data type field within the coprocessor number in the coprocessor instruction also serves to specify one of multiple data types to be used in the coprocessor operation; particular coprocessors can interpret this part of the coprocessor number to determine data type. If the coprocessor supports multiple data types, then it has multiple coprocessor numbers for which it will issue accept signals and then uses the data type field to control the data type used. If a coprocessor does not support a particular data type then it will not issue an accept signal for coprocessor instructions that specify that data type. The main processor can then use emulation code to provide support for that coprocessor instruction.

A diagnostic method for outputting diagnostic data relating to processing of instruction streams stemming from a computer program, at least some of said instructions streams comprising multiple threads is disclosed. The method comprises the steps of: (i) receiving diagnostic data; (ii) reordering said received diagnostic data in dependence upon reordering data, said reordering data comprising data relating to said computer program; and (iii) outputting said reordered diagnostic data. In general, the instructions streams are processed by a plurality of processing units arranged to process at least some of said instructions in parallel, said diagnostic data being received from said plurality of processing units.

A processor core for transitioning a debugging unit between a plurality of operating states in response to an instruction stream is disclosed. The processor core generates trace data as it processes operating signals of the instruction stream. The processor core provides a first trigger event signal to the debugging unit in response to a first trigger instruction signal within the instruction stream that is representative of a triggering instruction to transitions the debugging unit to a base operating state. The processor core provides a second trigger event signal to the debugging unit in response to a second trigger instruction signal within the instruction stream that is representative of a triggering instruction to dynamically store trace data within the memory component of the debugging unit. The processor core provides a third trigger event signal to the debugging unit in response to a third trigger instruction signal within the instruction stream that is representative of a triggering instruction to statically store trace data within the memory component of the debugging unit. Concurrently or alternatively, the processor core can provide one or more of the trigger event signals to the debugging unit as a function of a generated trigger data in response to additional operational instructions within the instruction stream.

A method and circuit arrangement provide support for a hybrid pipeline that dynamically switches between out-of-order and in-order modes. The hybrid pipeline may selectively execute instructions from at least one instruction stream that require the high performance capabilities provided by out-of-order processing in the out-of-order mode. The hybrid pipeline may also execute instructions that have strict power requirements in the in-order mode where the in-order mode conserves more power compared to the out-of-order mode. Each stage in the hybrid pipeline may be activated and fully functional when the hybrid pipeline is in the out-of-order mode. However, stages in the hybrid pipeline not used for the in-order mode may be deactivated and bypassed by the instructions when the hybrid pipeline dynamically switches from the out-of-order mode to the in-order mode. The deactivated stages may then be reactivated when the hybrid pipeline dynamically switches from the in-order mode to the out-of-order mode.

A circuit is provided to provide instruction streams to a processing device: embodiments of the circuit are appropriate for use with RISC CPUs, whereas other embodiments are useable with other processing devices, such as small processing devices used in a field programmable array. The circuit receives an external instruction stream which provides a first set of instruction values, and has a memory which contains a second set of instruction values. Two or more outputs provide instruction streams to the processing device. The circuit has a control input in the form of a mask which causes a selection means to allocate bits from the first and second sets of instruction values to different instruction streams to the processing device.

A source computer system with one instruction set architecture (ISA) is configured to run on a target hardware system that has its own ISA, which may be the same as the source ISA. In cases where the source instructions cannot be executed directly on the target system, the invention provides binary translation system. During execution from binary translation, however, both synchronous and asynchronous exceptions may arise. Synchronous exceptions may be either transparent (requiring processing action wholly within the target computer system) or non-transparent (requiring processing that alters a visible state of the source system). Asynchronous exceptions may also be either transparent or non-transparent, in which case an action that alters a visible state of the computer system needs to be applied. The invention includes subsystems, and related methods of operation, for detecting the occurrence of all of these types of exceptions, to handle them, and to do so with precise reentry into the interrupted instruction stream; by “precise” is meant that the atomic execution of the source instructions is guaranteed, and that the application of actions, including those that originate from asynchronous exceptions, occurs at the latest at the completion of the current source instruction at the time of the request for the action. The binary translation and exception-handling subsystems are preferably included as components of a virtual machine monitor which is installed between the target hardware system and the source system, which is preferably a virtual machine.

A prefetching technique referred to as future execution (FE) dynamically creates a prefetching thread for each active thread in a processor by simply sending a copy of all committed, register-writing instructions in a primary thread to an otherwise idle processor. On the way to the second processor, a value predictor replaces each predictable instruction with a load immediate instruction, where the immediate is the predicted result that the instruction is likely to produce during its nth next dynamic execution. Executing this modified instruction stream (i.e., the prefetching thread) in another processor allows computation of the future results of the instructions that are not directly predictable. This causes the issuance of prefetches into the shared memory hierarchy, thereby reducing the primary thread's memory access time and speeding up the primary thread's execution.

A microprocessor for efficient processing of instructions in a program flow including a conditional program flow control instruction, such as a branch instruction. The conditional program flow control instruction targets a first code section to be processed if the condition is resolved to be met, and a second code section to be processed if the condition is resolved to be not met. A fetch unit fetches instructions to be processed and branch prediction logic coupled to the fetch unit predicts the resolution of the condition. The branch prediction logic of the invention also determines whether resolution of the condition is unlikely to be predicted accurately. Stream management logic responsive to the branch prediction logic directs speculative processing of instructions from both the first and second code sections prior to resolution of the condition if resolution of the condition is unlikely to be predicted accurately. Results of properly executed instructions are then committed to architectural state in program order. In this manner, the invention reduces the performance penalty related to mispredictions.

A data processing apparatus is provided comprising first processing circuitry, second processing circuitry and shared processing circuitry. The first processing circuitry and second processing circuitry are configured to operate in different first and second power domains respectively and the shared processing circuitry is configured to operate in a shared power domain. The data processing apparatus forms a uni-processing environment for executing a single instruction stream in which either the first processing circuitry and the shared processing circuitry operate together to execute the instruction stream or the second processing circuitry and the shared processing circuitry operate together to execute the single instruction stream. Execution flow transfer circuitry is provided for transferring at least one bit of processing-state restoration information between the two hybrid processing units.

Autonomous selection between multiple virtualization techniques implemented in a virtualization layer of a virtualized computer system. The virtual machine monitor implements multiple virtualization support processors that each provide for the comprehensive handling of potential virtualization exceptions. A virtual machine monitor resident virtualization selection control is operable to select between use of first and second virtualization support processors dependent on identifying a predetermined pattern of temporally local privilege dependent instructions within a portion of an instruction stream as encountered in the execution of a guest operating system.

A computer system and method for compressing an instruction stream and executing the compressed instruction stream without decompression. The invention utilizes a new pointer instruction, i.e., an “Echo” instruction that is used to replace repeated instructions or sequences of instructions, also referred to as phrases. Replacing subsequent, repeated phrases with the Echo instruction reduces the size of the instruction stream, i.e., compresses the instruction stream. The Echo instruction generally identifies at least one literal instruction appearing before the Echo instruction and further identifies the number of instructions appearing before the Echo instruction to be repeated. No additional delimiters are necessary, e.g., no End Echo instructions are required. Omitting the End Echo instruction allows for overlapping phrases without the need for two Echo instructions. Reducing the number of instructions used significantly increases compression.

An apparatus for extracting instructions from a stream of undifferentiated instruction bytes in a microprocessor having an instruction set architecture in which the instructions are variable length. Decode logic decodes the instruction bytes of the stream to generate for each a corresponding opcode byte indictor and end byte indicator and receives a corresponding taken indicator for each of the instruction bytes. The taken indicator is true if a branch predictor predicted the instruction byte is the opcode byte of a taken branch instruction. The decode logic generates a corresponding bad prediction indicator for each of the instruction bytes. The bad prediction indicator is true if the corresponding taken indicator is true and the corresponding opcode byte indicator is false. The decode logic sets to true the bad prediction indicator for each remaining byte of an instruction whose opcode byte has a true bad prediction indicator. Control logic extracts instructions from the stream and sends the extracted instructions for further processing by the microprocessor. The control logic foregoes sending an instruction having both a true end byte indicator and a true bad prediction indicator.

A method, system, and computer program product for minimizing branch prediction latency in a pipelined computer processing environment are provided. The method includes detecting a branch loop utilizing branch instruction addresses and corresponding target addresses stored in a branch target buffer (BTB). The method also includes fetching the branch loop into a pre-decode instruction buffer and qualifying the branch loop for loop lockdown. The method further includes locking an instruction stream that forms the branch loop in the pre-decode instruction buffer and processing qualified branch loop instructions from the buffer and powering down instruction fetching and branch prediction logic (BPL) associated with the BTB.

A profile-based loop optimizer generates an execution frequency table for each loop that gives more detailed profile data that allows making a more intelligent decision regarding if and how to optimize each loop in the computer program. The execution frequency table contains entries that correlate a number of times a loop is executed each time the loop is entered with a count of the occurrences of each number during the execution of an instrumented instruction stream. The execution frequency table is used to determine whether there is one dominant mode that appears in the profile data, and if so, optimizes the loop according to the dominant mode. The optimizer may perform optimizations by peeling a loop, by unrolling a loop, and by performing both peeling and unrolling on a loop according to the profile data in the execution frequency table for the loop. In this manner the execution time of the resulting code is minimized according to the detailed profile data in the execution frequency tables, resulting in a computer program with loops that are more fully optimized.

An intelligent caching data structure and mechanisms for storing visual information via objects and data representing graphics information. The data structure is generally associated with mechanisms that intelligently control how the visual information therein is populated and used. The cache data structure can be traversed for direct rendering, or traversed for pre-processing the visual information into an instruction stream for another entity. Much of the data typically has no external reference to it, thereby enabling more of the information stored in the data structure to be processed to conserve resources. A transaction/batching-like model for updating the data structure enables external modifications to the data structure without interrupting reading from the data structure, and such that changes received are atomically implemented. A method and mechanism are provided to call back to an application program in order to create or re-create portions of the data structure as needed, to conserve resources.

Apparatus for processing data is provided, said apparatus comprising: a main processor 4 responsive to main processor instructions within a stream of instructions input to said main processor 4 to perform main processor operations; a coprocessor 6 coupled to said main processor 4 via a coprocessor interface CP and responsive to coprocessor instructions MCR, MRC within said stream of instructions to perform coprocessor operations; wherein said coprocessor 6 is a debug coprocessor operable to at least partially control generation of diagnostic data for debugging said apparatus for processing data and said coprocessor instructions are debug coprocessor instructions that control operation of said debug coprocessor. Using a debug mechanism in the form of a debug coprocessor reduces the impact of the debug mechanism upon normal operation.

Accelerating processing of a non-sequential instruction stream on a processor with multiple compute units by broadcasting to a plurality of compute units a generic instruction stream derived from a sequence of instructions; the generic instruction stream including an index section and a compute section; applying the index section to localized data stored in each compute unit to select one of a plurality of stored local parameter sets; and applying in each compute unit the selected set of parameters to the local data according to the compute section to produce each compute unit's localized solution to the generic instruction.

Embodiments of an apparatus, system and method enhance the efficiency of processor resource utilization during instruction prefetching via one or more speculative threads. Renamer logic and a map table are utilized to perform filtering of instructions in a speculative thread instruction stream. The map table includes a yes-a-thing bit to indicate whether the associated physical register's content reflects the value that would be computed by the main thread. A thread progress beacon table is utilized to track relative progress of a main thread and a speculative helper thread. Based upon information in the thread progress beacon table, the main thread may effect termination of a helper thread that is not likely to provide a performance benefit for the main thread.

Techniques are disclosed relating to a processor that is configured to execute control transfer instructions (CTIs). In some embodiments, the processor includes a mechanism that suppresses results of mispredicted younger CTIs on a speculative execution path. This mechanism permits the branch predictor to maintain its fidelity, and eliminates spurious flushes of the pipeline. In one embodiment, a misprediction bit is be used to indicate that a misprediction has occurred, and younger CTIs than the CTI that was mispredicted are suppressed. In some embodiments, the processor may be configured to execute instruction streams from multiple threads. Each thread may include a misprediction indication. CTIs in each thread may execute in program order with respect to other CTIs of the thread, while instructions other than CTIs may execute out of program order.

The present invention allows a microprocessor to identify and speculatively execute future load instructions during a stall condition. This allows forward progress to be made through the instruction stream during the stall condition which would otherwise cause the microprocessor or thread of execution to be idle. The data for such future load instructions can be prefetched from a distant cache or main memory such that when the load instruction is re-executed (non speculative executed) after the stall condition expires, its data will reside either in the L1 cache, or will be enroute to the processor, resulting in a reduced execution latency. When an extended stall condition is detected, load lookahead prefetch is started allowing speculative execution of instructions that would normally have been stalled. In this speculative mode, instruction operands may be invalid due to source loads that miss the L1 cache, facilities not available in speculative execution mode, or due to speculative instruction results that are not available via forwarding and are not written to the architected registers. A set of status bits are used to dynamically keep track of the dependencies between instructions in the pipeline and a bit vector tracks invalid architected facilities with respect to the speculative instruction stream. Both sources of information are used to identify load instructions with valid operands for calculating the load address. If the operands are valid, then a load prefetch operation is started to retrieve data from the cache ahead of time such that it can be available for the load instruction when it is non-speculatively executed.

A processor core includes an instruction decode unit that may dispatch a same integer instruction stream to a plurality of integer execution units and may consecutively dispatch a same floating-point instruction stream to a floating-point unit. The integer execution units may operate in lock-step such that during each clock cycle, each respective integer execution unit executes the same integer instruction. The floating-point unit may execute the same floating-point instruction stream twice. Prior to the integer instructions retiring, compare logic may detect a mismatch between execution results from each of the integer execution units. In addition, prior to the results of the floating-point instruction stream transferring out of the floating-point unit, the compare logic may also detect a mismatch between results of execution of each consecutive floating-point instruction stream. Further, in response to detecting any mismatch, the compare logic may cause instructions causing the mismatch to be re-executed.