Run-time selection of feed-back connections in a multiple-instruction word processor
A processing apparatus is arranged to execute multiple-instruction words, a multiple-instruction word having a plurality of instructions. The processing apparatus comprises a plurality of issue slots (IS 1 , IS 2 ) arranged for parallel execution of the plurality of instructions; a register file (RF 1 , RF 2 ) accessible by the plurality of issue slots, and a communication network (CN) for coupling of the plurality of issue slots and the register file. The processing apparatus is further arranged to produce a first identifier (OV 1 ) on the validity of first result data (RD 1 ) produced by a first issue slot (IS 1 ) and a second identifier (OV 2 ) on the validity of second result data (RD 2 ) produced by a second issue slot (IS 2 ). The communication network comprises at least one selection circuit (SC 1 ) arranged to dynamically control the transfer of either the first result data or the second result data to a register of the register file, in a single processor cycle, by using the first identifier and the second identifier.
1. A processing apparatus arranged to execute multiple-instruction words, a multiple-instruction word having a plurality of instructions, comprising:
i. a plurality of issue slots arranged for parallel execution of the plurality of instructions;
ii. a plurality of register files accessible by the plurality of issue slots;
iii. a communication network for coupling the plurality of issue slots and the register files,
iv. characterized in that the processing apparatus is further arranged to produce a first identifier on a validity of a first result data produced by a first issue slot and a second identifier on a validity of a second result data produced by a second issue slot,
v. in that the communication network comprises first selection circuits and second selection circuits arranged to dynamically control a selective write back of the first result data and the second result data to a register of the register files, in a single processor cycle, by using the first identifier and the second identifier,
vi. wherein the first selection circuits are coupled to outputs of the issue slots, respectively, and
vii. wherein the second selection circuits are coupled to inputs of the register files, wherein the first selection circuits select result data and output valid result data for transfer as selected result data and result valid signal via a communication channel to the second selection circuits, and wherein the second selection circuits dynamically select a valid result data from the selected result data using a value of a corresponding result value signal.
2. A processing apparatus according to claim 1 , characterized in that at least one of the first and the second selection circuits is further arranged to dynamically control the transfer of no result data to the register of the register files, in a single processor cycle, by using the first and the second identifier.
3. A processing apparatus according to claim 1 , characterized in that the communication network is arranged to transfer either the first result data or the second result data via a shared communication channel.
4. A processing apparatus according to claim 1 , characterized in that the first result data corresponds to a first conditional operation and the second result data corresponds to a second conditional operation, the first and second conditional operations having mutually exclusive conditions, and wherein the first identifier is set according to an evaluation of a condition of the first conditional operation and the second identifier is set according to an evaluation of a condition of the second conditional operation.
5. A processing apparatus according to claim 4 , characterized in that the first and second issue slots are arranged to produce the first identifier and the second identifier on the validity of the first and second result data, respectively.
6. A processing apparatus according to claim 1 , wherein at least one of the first and the second selection circuits is further arranged to statically control the transfer of either first result data from a first issue slot or second result data from a second issue slot, to the register files, using control information derived from a multiple-instruction word.
7. A processing apparatus according to claim 1 , characterized in that the register files is a distributed register file.
8. A processing apparatus according to claim 1 , characterized in that the communication network is a partially connected communication network.
9. A processing apparatus according to claim 1 , characterized in that least one of the first and the second selection circuits is further arranged to dynamically control a write back of at least a third result data to the register of the register files, in a single processor cycle, by using a corresponding identifier on a validity of result data.