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US 5,204,825 AGranted
Method and apparatus for exact leading zero prediction for a floating-point adder
AssigneeWeitek Corporation
InventorKenneth Ng
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Abstract
A leading zero predictor (LZP) in parallel with the full subtraction operation correctly predicts the exact number of leading zeros of a subtraction result. Once the full subtraction operation is completed, the necessary shifts may be performed immediately, without a delay to determine the presence of leading zeros, and without need for a normalization corrector.
Claims8
A normalization apparatus for determining a number of leading zeros of a result of an operation subtracting from a first operand a second operand, said apparatus comprising:
- a) means for grouping the bits of each operand in sets, each set of bits from the first operand being paired with a corresponding set of bits from the second operand;
- b) means, coupled to the set pairs, for performing setwise subtractions with the set pairs to produce a plurality of setwise subtraction results;
- c) means, coupled to the setwise subtraction performing means, for selecting one of said setwise results, for determining a need for a borrow from said selected setwise result, and for determining a number of setwise normalization shifts according to a position of said selected setwise result;
- d) means, coupled to the setwise shift determining means, for determining a number of bitwise normalization shifts from said selected setwise result and said need for a borrow from said selected setwise result.
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Dependencies are inferred from the claim text.