Sun Microsystems, Inc.

Choon-Ping Chng

Tzungren A Tzeng

A method of executing a fused instruction is disclosed. The method begins by performing several actions, which may be performed serially or in parallel. These include performing a floating point multiplication of a first floating point number by a second floating point number and normalizing a third floating point number. The floating point multiplication of the first and second floating point numbers generates a first result, while the normalization generates a second result. The first result is then added to the second result, generating an unnormalized result. A determination is also made as to whether a large exponent difference exists between the first result and the second result. If a large exponent difference exists between the first result and the second result, a large exponent difference normalization is performed on the unnormalized result. Otherwise, a small exponent difference normalization is performed on the unnormalized result.

Method and apparatus for performing fused instructions by determining exponent differences

A fused instruction datapath is disclosed. The fused instruction datapath may include a normalization unit, a floating point mutltiplier coupled to the normalization unit, and a mantissa alignment unit coupled to provide an aligned mantissa to the floating point multiplier. The floating point multiplier may include a term generation unit and a compensation unit coupled to the term generation unit. The term generation unit may be configured to generate a sum term and a carry term. The compensation unit may be configured to compensate the sum term.

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Sunnyvale, CA, United States of America

Choon-Ping Chng