Processing apparatus, processing method and compiler
Computer architectures consist of a fixed data path, which is controlled by a set of control words. Each control word controls part of the data path. Each set of instructions generates a new set of control words. In case of a VLIW processor, multiple instructions are packaged into one so-called VLIW instruction. A VLIW processor uses multiple, independent functional units to execute these multiple instructions in parallel. Application specific domain tuning of a VLIW processor requires that instructions having varying requirements with respect to the number of instruction bits they require can be encoded in a single VLIW instruction, such that an efficient encoding and encoding of instructions is maintained. The present invention describes a processing apparatus as well as a processing method for processing data, allowing the use of such an asymmetric instruction set. The processing apparatus comprises at least a first (UC 0 ) and a second issue slot (UC 3 ), wherein each issue slot comprises a plurality of functional units (FU 01 -FU 02 , FU 30 -FU 32 ). The first issue slot (UC 0 ) is being controlled by a first control word ( 411 ) being generated from a first instruction (InstrA) and the second issue slot is being controlled by a second control word ( 417 ) being generated from the second instruction (InstrD), the width of the first control word ( 411 ) being different from the width of the second control word ( 417 ). By varying the width of a corresponding control word, instructions requiring a different number of bits can be efficiently encoded in a VLIW instruction while allowing an efficient instruction decoding as well.
1. A processing apparatus, comprising:
an input means for inputting data;
a register file for storing said input data;
at least a first and a second issue slot, wherein each issue slot comprises a plurality of functional units;
and wherein the processing apparatus is conceived for processing data retrieved from the register file based on control signals generated from a set of instructions being executed in parallel, the set of instructions comprising at least a first and a second instruction, the first issue slot being controlled by a first control word corresponding to the first instruction and the second issue slot being controlled by a second control word corresponding to the second instruction,
characterized in that the width of the first control word is different from the width of the second control word.
2. An apparatus according to claim 1 , wherein said processing apparatus is a VLIW processor and wherein said set of instructions is grouped in a VLIW instruction.
3. An apparatus according to claim 2 , wherein the VLIW instruction is a compressed VLIW instruction, comprising dedicated bits for encoding of NOP operations.
4. An apparatus according to claim 3 , comprising a decompression means for decompressing the compressed VLIW instruction and wherein the decompression means is conceived to derive information on the control word width using the dedicated bits.
5. An apparatus according to claim 1 , which further comprises a connection network for coupling the register file and the issue slots.
6. An apparatus according to claim 2 , wherein the register file is a distributed register file.
7. An apparatus according to claim 1 , wherein the width of the first and the second control word is an integer multiple of a predetermined value.
8. A processing method for processing data, said method comprising the following steps:
storing input data in a register file;
processing data retrieved from the register file based on control signals generated from a set of instructions being executed in parallel, the set of instructions comprising at least a first and a second instruction, a first issue slot being controlled by a first control word corresponding to the first instruction and a second issue slot being controlled by a second control word corresponding to the second instruction,
and wherein the first and the second issue slot comprise a plurality of functional units,
characterized in that the width of the first control word is different from the width of the second control word.
9. A method according to claim 8 , wherein said set of instructions is grouped in a VLIW instruction.
10. A method according to claim 9 , wherein the VLIW instruction is a compressed VLIW instruction, comprising dedicated bits for encoding of NOP operations.
11. A method according to claim 10 , further comprising the step of decompressing the compressed VLIW instruction by means of a decompression means, and wherein the decompression means derives information on the control word width using the dedicated bits.