Mips Tech Limited

Advanced Micro Devices Corporation

Imagination Technologies Limited

Mips Technologies, Inc.

Ranganathan Sudhakar

Ranjit Joseph Rozario

Debjit Das Sarma

Parthiv Pota

Michael G Frank

Nhon Toai Quach

Sanjay Patel

Era Kasturia Nangia

Debasish Chandra

Debjit DasSarma

Daryl Lieu

Chris Dearman

Jonathan Choy

A method provides for decoding, in a microprocessor, an instruction into data identifying a first register, a second register, an immediate value, and an opcode identifier. The opcode identifier is interpreted as indicating that an arithmetic operation is to be performed on the first register and the second register, and that the microprocessor is to perform a change of control operation in response to the addition of the first register and the second register causing overflow or underflow. The change of control operation is to a location in a program determined based on the immediate value. A processor can be provided with a decoder and other supporting circuitry to implement such method. Overflow/underflow can be checked on word boundaries of a double-word operation.

Processor supporting arithmetic instructions with branch on overflow and methods

In an aspect, a processor supports modeless execution of 64 bit and 32 bit instructions. A Load/Store Unit (LSU) decodes an instruction that without explicit opcode data indicating whether the instruction is to operate in a 32 or 64 bit memory address space. LSU treats the instruction either as a 32 or 64 bit instruction in dependence on values in an upper 32 bits of one or more 64 bit operands supplied to create an effective address in memory. In an example, a 4 GB space addressed by 32-bit memory space is divided between upper and lower portions of a 64-bit address space, such that a 32-bit instruction is differentiated from a 64-bit instruction in dependence on whether an upper 32 bits of one or more operands is either all binary 1 or all binary 0. Such a processor may support decoding of different arithmetic instructions for 32-bit and 64-bit operations.

Modeless instruction execution with 64/32-bit addressing

A processor is configured to identify a branch instruction immediately followed by an architectural delay slot. A single bonded instruction comprising the branch instruction immediately followed by the architectural delay slot is created. The single bonded instruction is loaded into an instruction buffer.

Apparatus and method for bonding branch instruction with architectural delay slot

In one aspect, a processor has a register file, a private Level 1 (L1) cache, and an interface to a shared memory hierarchy (e.g., an Level 2 (L2) cache and so on). The processor has a Load Store Unit (LSU) that handles decoded load and store instructions. The processor may support out of order and multi-threaded execution. As store instructions arrive at the LSU for processing, the LSU determines whether a counter, from a set of counters, is allocated to a cache line affected by each store. If not, the LSU allocates a counter. If so, then the LSU updates the counter. Also, in response to a store instruction, affecting a cache line neighboring a cache line that has a counter that meets a criteria, the LSU characterizes that store instruction as one to be effected without obtaining ownership of the effected cache line, and provides that store to be serviced by an element of the shared memory hierarchy.

Processors and methods for cache sparing stores

A processor comprises a decoder for decoding an instruction based both on an explicit opcode identifier and on metadata encoded in the instruction. For example, a relative order of source register names may be used to decode the instruction. As an example, an instruction set may have a Branch Equal (BEQ) specifying two registers (r1 and r2) that store values that are compared for equality. An instruction set can provide a single opcode identifier for BEQ and a processor can determine whether to decode a particular instance of that opcode identifier as BEQ or another instruction, in dependence on an order of appearance of the source registers in that instance. For example, the BEQ opcode can be interpreted as a branch not equal, if a higher numbered register appears before a lower numbered register. Additional forms of metadata can include interpreting a constant included in an instruction, as well as determining equality of source registers, among other forms of metadata.

Processor with virtualized instruction set architecture and methods

In one aspect, a pipelined ECC-protected cache access method and apparatus provides that during a normal operating mode, for a given cache transaction, a tag comparison action and a data RAM read are performed speculatively in a time during which an ECC calculation occurs. If a correctable error occurs, the tag comparison action and data RAM are repeated and an error mode is entered. Subsequent transactions are processed by performing the ECC calculation, without concurrent speculative actions, and a tag comparison and read are performed using only the tag data available after the ECC calculation. A reset to normal mode is effected by detecting a gap between transactions that is sufficient to avoid a conflict for use of tag comparison circuitry for an earlier transaction having a repeated tag comparison and a later transaction having a speculative tag comparison.

Pipelined ECC-protected memory access

Methods and systems that identify and power up ways for future instructions are provided. A processor includes an n-way set associative cache and an instruction fetch unit. The n-way set associative cache is configured to store instructions. The instruction fetch unit is in communication with the n-way set associative cache and is configured to power up a first way, where a first indication is associated with an instruction and indicates the way where a future instruction is located and where the future instruction is two or more instructions ahead of the current instruction.

Way lookahead

A computer includes a memory and a processor connected to the memory. The processor includes memory segment configuration registers to store defined memory address segments and defined memory address segment attributes such that the processor operates in accordance with the defined memory address segments and defined memory address segment attributes to allow kernel mode access to user space virtual addresses for enhanced kernel mode memory capacity.

Processor with kernel mode access to user space virtual addresses

A processor includes a computation engine to produce a computed value for a set of operands. A cache stores the set of operands and the computed value. The cache is configured to selectively identify a match and a miss for a new set of operands. In the event of a match the computed value is supplied by the cache and a computation engine operation is aborted. In the event of a miss a new computed value for the new set of operands is computed by the computation engine and is stored in the cache.

Apparatus and method for operating a processor with an operation cache

A processor includes a decode unit and a byte permute unit. The byte permute unit receives an instruction from the decode unit. The byte permute unit determines whether the instruction corresponds to a shuffle instruction or a shift instruction. For a shuffle instruction, the byte permute unit uses a byte shuffler to perform a shuffle operation indicated by the instruction. For a shift instruction that indicates a shift magnitude, the byte permute unit uses the byte shuffler to byte-level shift a source operand corresponding to the instruction by an integer number of bytes. The byte permute unit also generates a sequence of output bits by bit-shifting the byte-level shifted source operand by a number of bits such that the sum of the number of bits and the integer number of bytes is equal to the shift magnitude.

Combined byte-permute and bit shift unit

A system and method for increasing processor throughput by decreasing a loop critical path. In one embodiment, a table comprises multiple stack entries, each comprising an x87 floating-point (FP) stack specifier. The combinatorial logic for operand translation of N FP instructions per clock cycle may require N instantiated copies of a combinatorial logic block. Each instantiated copy may determine a new ordering of the stack entries. Control logic may receive necessary information from the corresponding N FP instructions and determine a corresponding combined computational effect, or stack reordering, on entries within the table based on two or more instructions. Resulting control signals are conveyed to the N instantiated copies. A resulting accumulative delay from an input of the first copy to the output of the Nth copy may be less than or equal to (N&#x2212;1)*time_delay versus a longer N*time_delay.

Superscalar register-renaming for a stack-addressed architecture

A system and method for efficient reliable execution on a simultaneous multithreading machine. A processor is placed in a reliable execution mode (REM) to detect possible errors during execution of a software application. Only two threads may be configured to operate in this mode. Floating-point store and integer-transfer unary instructions may be converted to new instructions. Each new instruction has two source operands, each corresponding to a different thread is specified by a same logical register number as a single source operand of the original unary instruction. All other instructions are replicated, wherein the original instruction and its twin are assigned to different threads. Simultaneous multi-threaded (SMT) floating-point logic may only be able to provide lockstep execution when it communicates using the new instruction with instantiated integer independent clusters. The new instruction cannot begin until both source operands are ready, which are subsequently compared to determine any mismatches or errors.

Reliable execution using compare and transfer instruction on an SMT machine

A method and apparatus are contemplated for increasing the number of available instructions in an instruction set architecture. The new instructions extend the number of general-purpose registers and include three or more operands. A combination of an escape code field, an opcode field, an operation configuration field and an operation size field determines a unique new instruction operation. A source operand extension field includes bits to be combined with other fields in order to extend the number of source operand values for general-purpose registers.

Growing community of inventors

Santa Clara, CA, United States of America

Ranganathan Sudhakar