Encoding and decoding variable length instructions
AssigneeImagination Technologies Limited
InventorsSimon Thomas Nield, James McCarthy
Life of this patent
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Abstract
Methods of encoding and decoding are described which use a variable number of instruction words to encode instructions from an instruction set, such that different instructions within the instruction set may be encoded using different numbers of instruction words. To encode an instruction, the bits within the instruction are re-ordered and formed into instruction words based upon their variance as determined using empirical or simulation data. The bits in the instruction words are compared to corresponding predicted values and some or all of the instruction words that match the predicted values are omitted from the encoded instruction.
Claims15
Decoding hardware comprising:
- hardware logic configured to determine an encoding type from a fetched instruction word;
- word selection logic configured to generate an ordered sequence of instruction words by selecting, for each of the instruction words in the sequence, either the fetched instruction word or a predicted instruction word, and to concatenate the instruction words in the ordered sequence to form an encoded instruction;
- re-order hardware logic configured to re-order bits in the encoded instruction to generate a decoded instruction;
- and
- an output arranged to output the decoded instruction.
A method of decoding instructions comprising:
- determining an encoding type from a fetched instruction word;
- generating an ordered sequence of instruction words by selecting, for each of the instruction words in the sequence, the fetched instruction word or a predicted instruction word;
- concatenating the instruction words in the ordered sequence to form an encoded instruction and re-ordering bits in the encoded to generate a decoded instruction;
- and
- outputting the decoded instruction.
Dependencies are inferred from the claim text.