149 results about "Register renaming" patented technology

One embodiment of the present invention provides a system that facilitates precise exception semantics. The system includes a processor that uses register rename maps to support out-of-order execution, where the register rename maps track mappings between native architectural registers and physical registers for a program executing on the processor. These register rename maps include: 1) a working rename map that maps architectural registers associated with a decoded instruction to corresponding physical registers; 2) a retire rename map that tracks and preserves a set of physical registers that are associated with retired instructions; and 3) a checkpoint rename map that stores a mapping between a set of architectural registers and a set of physical registers for a preceding checkpoint in the program. When the program signals an exception, the processor uses the checkpoint rename map to roll back program execution to the preceding checkpoint.

A method for implementing a register renaming scheme for a digital data processor using a plurality of physical register files for supporting out-of-order execution of a plurality of instructions from one or more threads, the method comprising: using a DEF table to store the instruction dependencies between the plurality of instructions using the instruction tags, the DEF table being indexed by a logical register name and including one entry per logical register; using a rename USE table indexed by the instruction tags to store logical-to-physical register mapping information shared by multiple sets of different types of non-architected copies of logical registers used by multiple threads; using a last USE table to transfer data of the multiple sets of different types of non-architected copies of logical registers into the first set of architected registered files, the last USE table being indexed by a physical register name in the second set of rename registered files; and performing the register renaming scheme at the instruction dispatch or wake-up/issue time.

A single rename register array is used in an SMT processor. Two bits are added to each register address of the rename register array, one for bit for thread zero (CTB0) and one bit for thread one (CTB1). The CTB bits are all set to a logic value on power on or start-up. A control instruction (CI) that sets control bits used by other instructions is assigned a register in the rename register array having an address designated as pointer (PTR) address. When a control instruction with an assigned entry with PTR address M completes, then the CTB bit at the PTR address M is flipped to its opposite logic state; likewise, its Valid bit is set to a “not” Valid state. The self resetting CTB bit is used to determine whether an issued instruction sources a register in the rename register array or a corresponding architected register.

Control logic for storing values relating to unresolved exception instructions within a buffer to enable a register renaming table within a processor to be restored following an exception is disclosed. The processor is operable to process a stream of instructions from an instruction set, the instruction set comprising exception instructions and non-exception instructions, exception instructions being instructions that may generate an exception and non-exception instructions being instructions that execute in a statically determinable way. The processor comprises a physical set of registers operable to store data values being processed by the processor; and register renaming logic operable to receive a stream of decoded instructions and to map for each decoded instruction within the stream of decoded instructions, registers from an architectural set of registers associated with the instruction set to registers within the physical set of registers in dependence upon renaming values stored in the register renaming table; the control logic comprising a buffer and being operable: to identify exception and non-exception instructions within the decoded instruction stream and to group any non-exception instructions with a closest preceding exception instruction; to store in the buffer, register renaming values relating to any registers whose data values are modified by the group of instructions and which are renamed by the register renaming logic as a bundle of register renaming values associated with the exception instruction.

A unified register rename mechanism for targets of different instruction types is provided in a microprocessor. The universal rename mechanism renames destinations of different instruction types using a single rename structure. Thus, an instruction that is updating a floating point register (FPR) can be renamed along with an instruction that is updating a general purpose register (GPR) or vector multimedia extensions (VMX) instructions register (VR) using the same rename structure because the number of architected states for GPR is the same as the number of architected states for FPR and VR. Each destination tag (DTAG) is assigned to one destination. A floating point instruction may be assigned to a DTAG, and then a fixed point instruction may be assigned to the next DTAG and so forth. With a universal rename mechanism, significant silicon and power can be saved by having only one rename structure for all instruction types.

A system and method for reducing the latency of load operations. A register rename unit within a processor determines whether a decoded load instruction is eligible for conversion to a zero-cycle load operation. If so, control logic assigns a physical register identifier associated with a source operand of an older dependent store instruction to the destination operand of the load instruction. Additionally, the register rename unit marks the load instruction to prevent it from reading data associated with the source operand of the store instruction from memory. Due to the duplicate renaming, this data may be forwarded from a physical register file to instructions that are younger and dependent on the load instruction.

A method, processor, and computer program product employing an intermediate register mapper within a register renaming mechanism. A logical register lookup determines whether a hit to a logical register associated with the dispatched instruction has occurred. In this regard, the logical register lookup searches within at least one register mapper from a group of register mappers, including an architected register mapper, a unified main mapper, and an intermediate register mapper. A single hit to the logical register is selected among the group of register mappers. If an instruction having a mapper entry in the unified main mapper has finished but has not completed, the mapping contents of the register mapper entry in the unified main mapper are moved to the intermediate register mapper, and the unified register mapper entry is released, thus increasing a number of unified main mapper entries available for reuse.

The invention relates to a register renaming system and method for managing and renaming registers. The invention specifically provides the register renaming system for managing and renaming the registers by adopting multiple renamed register queues, and the system comprises a physical register group, a register alias table (RAT), an architecture register mapping table (ARMT), a select finger of the renamed register queues, a decoder, a logic register renaming device, an RAT modifying device and an updating device of the renamed register queues. In addition, the invention further provides the method for managing and renaming the registers by adopting the multiple renamed register queues. According to the technical scheme provided by the invention, renaming operation can be simultaneously performed on the multiple registers within a same period, the implementation method is simple, the time cost is small, and the register renaming system and method are suitable for superscalar microprocessors with higher transmission width.

A system and method for reducing the latency of data move operations. A register rename unit within a processor determines whether a decoded move instruction is eligible for a zero cycle move operation. If so, control logic assigns a physical register identifier associated with a source operand of the move instruction to the destination operand of the move instruction. Additionally, the register rename unit marks the given move instruction to prevent it from proceeding in the processor pipeline. Further maintenance of the particular physical register identifier may be done by the register rename unit during commit of the given move instruction.

The invention provides a method for renaming a status register in a superscalar processor with a pipeline structure, wherein the status register is a register composed of a plurality of flag bits selected from all flag bits of a flag register. The method comprises determining whether a microcode will read the status register when the microcode coded by a command reaches a register renaming module of the processor; if determining that the microcode will read the status register, allocating a nearest mapping physical register for the status register; otherwise, not allocating the physical register for the status register; determining whether the microcode will be written to the status register; if determining that the microcode will be written into the status register, allocating a new physical register with empty status to the status register; and otherwise, not allocating the physical register for the status register.

A data processing apparatus 2 supports out-of-order processing register renaming using a renaming stage 8. A set of physical registers 16 is mapped to architectural registers. Available-register identifying logic 26 is used to identify which physical registers 16 are available for use by the renaming stage 8. The available-register identifying logic 26 includes an instruction FIFO 28 storing register mapping data for unresolved instructions and indicating physical registers 16 storing data values which may be required in association with those unresolved speculative instructions. The speculative instructions may be predicted branch instructions, load/store instructions, conditional instructions or other types of instruction.

Within a data processing system 2 including a register renaming mechanism 8, 22, register renaming for some conditional instructions which are predicted as not-executed is suppressed. The conditional instructions which are subject to such suppression of renaming may not be all conditional instructions, but may be those which are known to consume a particularly large number of physical registers 24 if they are subject to renaming A conditional load multiple instruction in which multiple registers are loaded with new data values taken from memory in response to signal instruction is an example where the present technique may be used, particularly when one of the registers loaded is the program counter and accordingly the instruction is a conditional branch.

A method and circuit arrangement utilize a general purpose processing unit having a low power DSP mode for reconfiguring the general purpose processing unit to efficiently execute DSP workloads with reduced power consumption. When in a DSP mode, one or more of a data cache, an execution unit, and simultaneous multithreading may be disabled to reduce power consumption and improve performance for DSP workloads. Furthermore, partitioning of a register file to support multithreading, and register renaming functionality, may be disabled to provide an expanded set of registers for use with DSP workloads. As a result, a general purpose processing unit may be provided with enhanced performance for DSP workloads with reduced power consumption, while also not sacrificing performance for other non-DSP/general purpose workloads.

Techniques for handling dependency conditions, including evil twin conditions, are disclosed herein. An instruction may designate a source register comprising two portions. The source register may be a double-precision register and its two portions may be single-precision portions, each specified as destinations by two other single-precision instructions. Execution of these two single-precision instructions, especially on a register renaming machine, may result in the appropriate values for the two portions of the source register being stored in different physical locations, which can complicate execution of an instruction stream. In response to detecting a potential dependency, one or more instructions may be inserted in an instruction stream to enable the appropriate values to be stored within one physical double precision register, eliminating an actual or potential evil twin dependency. Embodiments including a compiler that inserts instructions in a generated instruction stream to eliminate dependency conditions are also contemplated.

A microprocessor with a floating point unit configured to efficiently allocate multi-pipeline executable instructions is disclosed. Multi-pipeline executable instructions are instructions that are not forced to execute in a particular type of execution pipe. For example, junk ops are multi-pipeline executable. A junk op is an instruction that is executed at an early stage of the floating point unit's pipeline (e.g., during register rename), but still passes through an execution pipeline for exception checking. Junk ops are not limited to a particular execution pipeline, but instead may pass through any of the microprocessor's execution pipelines in the floating point unit. Multi-pipeline executable instructions are allocated on a per-clock cycle basis using a number of different criteria. For example, the allocation may vary depending upon the number of multi-pipeline executable instructions received by the floating point unit in a single clock cycle.

A register renaming system for out-of-order execution of a set of reduced instruction set computer instructions having addressable source and destination register fields, adapted for use in a computer having an instruction execution unit with a register file accessed by read address ports and for storing instruction operands. A data dependance check circuit is included for determining data dependencies between the instructions. A tag assignment circuit generates one or more tags to specify the location of operands, based on the data dependencies determined by the data dependance check circuit. A set of register file port multiplexers select the tags generated by the tag assignment circuit and pass the tags onto the read address ports of the register file for storing execution results.

Certain embodiments of the present invention are configured to facilitate analyzing computer code more efficiently. For example, by conducting a first level abstraction (e.g., symbolic interpretation and algebraic simplification) and a second level abstraction (e.g., generalization) of the computer code, the analysis may more accurately account for variations in the code that may occur as a result of register renaming, instruction reordering, choice of instructions, etc. while minimizing the cost of computations required to perform the analysis.

A system and method for reducing latency and power of register renaming. A free list in processor includes multiple banks for indicating availability of register identifiers used for register renaming. A register rename unit receives one or more destination architectural registers to rename with physical register identifiers. Responsive to determining the multiple banks within the free list are unbalanced with available physical register identifiers, one or more returning physical register identifiers are assigned to the destination architectural registers before assigning any physical register identifiers from any bank of the multiple banks with a lowest number of available physical register identifiers. A returning physical register identifier is a physical register identifier that is available again for assignment to a destination architectural register but not yet indicated in the free list as available. Each of the banks includes a single bit width decoded vector for indicating availability of given physical register identifiers.

The invention discloses an execution method for a logarithmic loading instruction. The method comprises the steps of extracting an LDP instruction, splitting the LDP instruction into two micro-operations with destination registers, performing decoding, register renaming and assignment by taking the micro-operations as units, assigning items for the two micro-operations in a reorder buffer during assignment, and combining the two micro-operations in a transmission queue; if two data loading pipelines are available, transmitting an LDP after combination to an memory access unit, and performing execution in the first data loading pipeline; after the execution, writing back a low half part of obtained data to the first destination register through a result bus of the first data loading pipeline, and writing back a high half part to the second destination register through a result bus of the second data loading pipeline; and finally submitting the two micro-operations to release resources.On the premise that data access times are not increased, the number of destination register channels can be reduced, the design complexity can be lowered, and the area expenditure can be reduced.