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394f993e75
This implements frsqrte by table lookup. We first normalize the input if necessary and adjust so that the exponent is even, giving us a mantissa value in the range [1.0, 4.0), which is then used to look up an entry in a 768-entry table. The 768 entries are appended to the table for reciprocal estimates, giving a table of 1024 entries in total. frsqrtes is implemented identically to frsqrte. The estimate supplied is accurate to 1 part in 1024 or better. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>