Instruction storage method with a compressed format using a mask word
AssigneeDigital Equipment Corporation
InventorsRobert P. Colwell, John O'Donnell, David B. Papworth, Paul K. Rodman
Life of this patent
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Abstract
A method and apparatus for storing an instruction word in a compacted form on a storage media, the instruction word having a plurality of instruction fields, features associating with each instruction word, a mask word having a length in bits at least equal to the number of instruction fields in the instruction word. Each instruction field is associated with a bit of the mask word and accordingly, using the mask word, only non-zero instruction fields need to be stored in memory. The instruction compaction method is advantageously used in a high speed cache miss engine for refilling portions of instruction cache after a cache miss occurs.
Claims9
A method for storing instruction words in a compressed format in a storage element of a data processor, each of the instruction words having N instruction fields, the method comprising the steps, performed by the data processor, of:
- designating a plurality of mask words, one mask word corresponding to each of the instruction words, wherein each mask word has a length at least equal to N bits;
- assigning each of the N instruction fields in each of the instruction words to one of the N bits of the corresponding mask word;
- setting each of the N bits of each corresponding mask word to a first designation when its assigned instruction field is a non-zero instruction field;
- setting each of the N bits of each corresponding mask word to a second designation when its assigned instruction field is a zero instruction field;
- and
- storing each mask word and each corresponding non-zero instruction field in the storage element as a representation of the instruction words.
A method for storing a plurality of very long instruction words in a compressed format in a data processor, wherein each of the instruction words has a plurality of instruction fields, the method comprising steps, performed by the data processor, of:
- assigning a corresponding mask word to each of the plurality of instruction words, wherein each bit of the corresponding mask word is assigned to an instruction field of the instruction word;
- setting each assigned bit of the corresponding mask word to a first designation when the assigned instruction field is a non-zero field;
- setting each assigned bit of the corresponding mask word to a second designation when the assigned instruction field is a zero field;
- and
- storing each corresponding mask word and each non-zero field in the storage element of the data processor.
Dependencies are inferred from the claim text.