Methods and apparatus for establishing port priority functions in a VLIW processor
Port priorities are defined on a 32-bit word, 16-bit half-word, and 8-bit byte basis to control the write enable signals to a compute register file (CRF). With a manifold array (ManArray) reconfigurable register file, it is possible to have double-word 64-bit and single word 32-bit data-type instructions mixed with other double-word, single-word, half-word, or byte data-type instructions within the same very long instruction word (VLIW). By resolving a write priority conflict on the byte, half-word, or word that is in conflict during the VLIW execution, it is possible to have partial operations complete that provide a useful function. For example, a load half-word to the half-word H 0 portion of a 32-bit register R 0 can have priority to complete its operation while a 64-bit shift of the register pair R 0 and R 1 will complete its operation on the non-conflicting half-word portions of the 64-bit register R 0 and R 1. Other unique capabilities result from the present approach to assigning port priorities that improve the performance of the ManArray indirect VLIW processor.
1. A processing apparatus comprising:
a memory register storage device comprising a first portion and a second portion;
a processing element comprising a first execution unit and a second execution unit for reading from and writing to the memory register storage device; and
port priority control logic for resolving a write conflict occurring when the first execution unit attempts to write to both the first portion and the second portion, and the second execution unit attempts to write to the second portion,
said port priority control logic allowing the first execution unit to write to the first portion,
said port priority control logic allowing the first execution unit to write to the second portion if the first execution unit has a higher port priority than the second execution unit,
said port priority control logic allowing the second execution unit to write to the second portion if the second execution unit has higher port priority than the first execution unit.
2. The processing apparatus of claim 1 wherein the bit width of the first portion equals the bit width of the second portion.
3. The processing apparatus of claim 1 wherein the port priority is programmable.
4. The processing apparatus of claim 1 wherein the memory register storage device is a computer register file.
5. The processing apparatus of claim 1 wherein the processing elements reading a very long instrisction word (VLIW) to determine whether to write to the first or second portion.
6. The processing apparatus of claim 1 wherein the processing element thither comprises a third execution unit, the third execution unit completing a write operation to the memory register storage device white conflicting write operations are prioritized for completion.
7. A method for resolving write conflicts between a first execution unit and a second execution unit disposed in a processing element, the method comprising:
providing a memory register storage device comprising a first portion and a second portion;
assigning a first port priority to the first execution unit;
assigning a second port priority to the second execution unit; and
resolving a write conflict occurring when the first execution unit attempts to write to both the first portion and the second portion, and the second execution unit attempts to write to the second portion, the resolving step further comprises
allowing the first execution unit to write to the first portion,
allowing the first execution unit to write to the second portion if the first execution unit has a higher port priority than the second execution unit,
allowing the second execution unit to write to the second portion if the second execution unit has a higher port priority than the first execution unit.
8. The method of claim 7 wherein the bit width of the first portion equals the bit width of the second portion.
9. The method of claim 7 wherein the first port priority is programmable.
10. The method of claim 7 wherein the memory register storage device is a computer register file.
11. The method of claim 7 wherein the resolving step further comprises reading every long instruction word (VLIW) to determine whether to write to the first or second portion.
12. The method of claim 7 wherein the processing element further comprises a third execution unit, the method further comprising completing a write operation to the memory register storage device while conflicting write operations are prioritized for completion.