Fujitsu Corporation

Ryohei Okazaki

Yasunobu Akizuki

Norihito Gomyo

Takashi Suzuki

Atushi Fusejima

Sota Sakashita

Hisanari Fujita

Takekazu Tabata

Chunye You

An arithmetic processing device executes instructions by pipeline processing. In the arithmetic processing device, a branch predictor includes a prediction holder holding a prediction value of a consecutively taken branch count, a current taken branch count, and a prediction value of a remaining taken branch count for conditional branch instructions. A branch instruction issuance scheduler outputs an instruction refetch request upon a branch prediction miss of a conditional branch instruction held at an entry other than a head of a branch instruction completion queue holding branch instructions to be completed, and a repair request to the branch predictor for conditional branch instructions held between the entry and the head of the queue. In response to the requests, the branch predictor updates the prediction value of the remaining taken branch count for the conditional branch instructions corresponding to the repair request.

Arithmetic processing device and arithmetic processing method

A processor configured to store prediction information that is obtained from a call instruction that is fetched in a RAS fetch, acquire the prediction information that is used in a return instruction from the RAS fetch, delete the prediction information, store the prediction information in a RAS complete after completion of execution of the call instruction, and delete the prediction information from the RAS complete after completion of execution of the return instruction, and specify a first entry that is the closest to a top of the queue among the entries in which the branch instruction on which the branch prediction error is detected is re-executed, store and delete the prediction information in and from the RAS fetch according to the call instruction and the return instruction that are stored in entries closer to the top than the first entry is, and cause the first entry to be re-executes.

Processing call and return information due to a branch prediction error

An arithmetic processing apparatus includes two instruction decoders. A first decoder processes instructions in a single cycle, while a second decoder processes instructions in a plurality of cycles. The apparatus further includes a determination circuit that causes the first decoder to process an instruction to be processed when the instruction to be processed is a specific instruction and there is no previous instruction being processed, and causes the second decoder to process the instruction to be processed when the instruction to be processed is not the specific instruction or there is a previous instruction being processed.

Arithmetic processing apparatus using either simple or complex instruction decoder

An arithmetic processing circuit includes an fetch unit configured to generate fetch addresses, an address table configured to store a branch address and a first tag for each of a plurality of indexes, the indexes being a first bit string extracted from a fetch address by including at least one bit among instruction address bits whose values vary within one fetch line, the first tag being a second bit string situated at higher bit positions than the first bit string, an upper tag storage unit configured to store a second tag situated at higher bit positions than the first tag, and a branch determination unit configured to supply to the fetch unit the branch address retrieved from the address table, upon determining that the first tag retrieved from the address table and the second tag in the upper tag storage unit match respective portions of the fetch address.

Arithmetic processing circuit and arithmetic processing method

A processing device performs a first process in a plurality of cycles to update a plurality of resources included in programmable resources. The processing device includes an instruction execution circuit that records that the first process is being executed, and makes an error notification when an error is detected during execution of an instruction, and a retry control circuit that records a type of the first process at a starting point of the first process, judges from the recorded type whether the first process is re-executable upon receiving the error notification during the first process, and instructs re-execution of the first process from a start of the first process in a case where the first process is judged to be re-executable. The instruction execution circuit performs a retry process to re-execute the first process when instructed from the retry control circuit to re-execute the first process.

Processing device and method of controlling processing device

An arithmetic processing device includes: a decoder configured to write an immediate value to a register in a case where an instruction to be executed is an instruction not involving data reading from the register; and a processor configured to read data from the register and write a computing result based on the read data to the register in a case where an instruction to be executed by the decoder is an instruction involving data reading from the register.

Arithmetic processing device

An arithmetic processing unit includes an instruction decoder which decodes a fetch instruction to issue an execution instruction; a reservation station which temporarily stores the execution instruction; and an arithmetic unit which executes the execution instruction, and the fetch instruction includes a multi-flow instruction which is divided into divided instructions and a single instruction. The instruction decoder includes: a pre-decoder including N number of slots each of which divides the multi-flow instruction into divided instructions; a main decoder including N number of slots each of which decodes the instructions to issue an execution instruction; and a pre-decoder buffer including N&#x2212;K number of slots each of which temporarily stores instructions in the pre-decoder. The instruction decoder repeats transferring the divided instructions and the single instructions from the slots of the pre-decoder and the slots of the pre-decoder buffer to the main decoder as much as possible in order.

Arithmetic processing unit and control method for arithmetic processing unit

An arithmetic processing unit includes an instruction decoder, first to fourth reservation stations, first and second computing units, first and second load-store units, and an allocation unit. The allocation unit, when the execution instruction is a first instruction that is executable in first and second computing units but not executable in first and second load-store units, allocates the first instruction to first or second reservation station based on a first allocation table, and when the execution instruction is a second instruction that is executable in the first and second load-store units but not executable in the first and second computing units, allocates the second instruction to third or fourth reservation station based on a second allocation table.

An arithmetic processing device includes: a decoding circuit configured to decode a command; a command execution circuit configured to execute the command decoded by the decoding circuit; a register circuit configured to include a plurality of registers for holding data used by the command execution circuit; an identification information holding circuit configured to store identification information for identifying a register for writing a specific value when the command is a register writing command; a setting circuit configured to hold the specific value; and an operation control circuit configured to execute inhibiting processing when the command is a register reading command, the inhibiting processing including inhibiting an access of the register by the register reading command and selecting the specific value held in the setting circuit.

Arithmetic processing device and control method implemented by arithmetic processing device

A processing device includes an instruction extractor that extracts target instructions intended for a loop process that is repeatedly performed, from instructions decoded by an instruction decoder, and a loop buffer including entries where each of the target instructions extracted by an instruction extractor are stored. An instruction processor stores a target instruction into one of the entries of the loop buffer, and combines target instructions into one target instruction in a case where resources of an instruction execution circuit used by the target instructions do not overlap, to store the one instruction in one of the entries of the loop buffer, and a selector selects the instruction output from the instruction decoder or the target instruction output from the loop buffer, and outputs the selected instruction to the instruction execution circuit.

An arithmetic processing device includes: a pipeline circuit including an instruction fetch circuit, an instruction decoder that performs a first branch misprediction determination for a branch instruction, and issues the instructions in-order, a branch instruction processing circuit which performs a second branch misprediction determination for the branch instruction; and a commit processing circuit that executes a commit processing of the processed instructions in-order. When a branch misprediction is established in the first branch misprediction determination, the instruction decoder inhibits issuing of the instructions to the branch prediction destination from the instruction decoder, and when the first branch instruction for which the branch misprediction is established is inputted, the branch instruction processing circuit clears the pipeline state in the instruction decoder, allows the instruction fetch circuit to start fetching instructions to a correct branch destination, and releases the inhibit of issuing of the instructions from the instruction decoder.

Arithmetic processing device and control method for arithmetic processing device

An arithmetic circuit performs a floating-point operation. A floating-point register includes entries each allocated to an architectural register or a renaming register. An operation execution controller circuit issues a floating-point operation instruction and outputs a termination report of the floating-point operation before the floating-point operation is terminated. When exception handling is not performed at the time of instruction completion even when an exception is detected in the operation of the floating-point operation instruction, an instruction completion controller circuit outputs a release instruction that indicates a release of a renaming register when instruction execution is completed after the termination report is received. An instruction decoder circuit receives the release instruction, allocates a first entry allocated to an architectural register that stores an execution result of the floating-point operation to a renaming register, and allocates a second entry allocated to a renaming register in the floating-point operation to the architectural register.

Releasing rename registers for floating-point operations

An arithmetic processing device includes a plurality of arithmetic processing units each including, an internal circuit that, in an instruction processing state in which an instruction is processed, processes the instruction and that, in an instruction processing stopped state in which instruction processing is stopped, transitions to a state of power save operation, and a power control circuit that disables the power save operation; and a monitoring circuit that monitors the instruction processing stopped state of the plurality of arithmetic processing units and counts the number of the arithmetic processing units in the instruction processing stopped state. The power control circuit of each of the plurality of arithmetic processing units disables the power save operation of the arithmetic processing unit in the instruction processing stopped state, in a case where the number of the arithmetic processing units in the instruction processing stopped state exceeds a threshold.

Arithmetic processing device and method of controlling arithmetic processing device

An arithmetic processing device includes: a branch prediction unit configured to predict a branch destination address and loop processing based on an address generated by an address generation unit; an instruction buffer unit configured to store an instruction of the address generated by the address generation unit; an instruction decoding unit configured to decode the instruction stored in the instruction buffer unit; and a loop buffer unit configured to store decoding results or decoding intermediate results of instructions of the predicted loop processing that are decoded by the instruction decoding unit and output the stored decoding results or decoding intermediate results a predetermined number of times in response to the loop processing, in which during a period when selecting the output of the loop buffer unit, operations of the address generation unit, the branch prediction unit, the instruction buffer unit, and the instruction decoding unit are stopped.

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Kawasaki, Japan

Ryohei Okazaki