Speculative load of look up table entries based upon coarse index calculation in parallel with fine index calculation
First Claim
1. A computer implemented method for accessing data in a look up table at locations in a memory determined by an index comprising the steps of:
- dividing the index into a coarse index requiring a first amount of calculation and a fine index requiring a second amount of calculation greater than said first amount;
calculating said coarse index;
fetching plural look up table entries from a memory to a data register file corresponding to said coarse index;
while said plural look up table entries are being transferred from said memory to said data register file, calculating said fine index;
determining the look up table entry corresponding to a combination of said coarse index and said fine index; and
extracting said determined look up table entry from said data register file.
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Abstract
A computer implemented method accesses data in a look up table via an index divided into a coarse index and a fine index. The method calculates the coarse index and fetches plural look up table entries. While the fetch is in progress, the method calculates the fine index. The method determines and extracts the look up table entry corresponding to the combined coarse and fine indexes Fetching plural look up table entries includes executing a single word load instruction, a doubleword load instruction or a pair of sequential or simultaneous single word load instructions. Extracting the look up table entry may include a section select move instruction, an extract and zero-extend a bit field instruction or a shift and mask operation.
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Citations
19 Claims
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1. A computer implemented method for accessing data in a look up table at locations in a memory determined by an index comprising the steps of:
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dividing the index into a coarse index requiring a first amount of calculation and a fine index requiring a second amount of calculation greater than said first amount;
calculating said coarse index;
fetching plural look up table entries from a memory to a data register file corresponding to said coarse index;
while said plural look up table entries are being transferred from said memory to said data register file, calculating said fine index;
determining the look up table entry corresponding to a combination of said coarse index and said fine index; and
extracting said determined look up table entry from said data register file. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification