Execution Units Are Often Pipelined

Re:Execution Units Are Often Pipelined by bonzini on Monday December 30, 2024 @02:31PM (#42552600)

Probably to do multiplies, as the extra add is basically free. Adds are cheaper.

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Re:Execution Units Are Often Pipelined by thesz on Monday December 30, 2024 @05:14PM (#42554126)

Adds are cheaper only for fixed-point computations. Floating point addition needs to denormalize one of its' arguments, perform an (integer) addition and then normalize the result.

Usually FP adds take a cycle or two longer than FP multiplication.

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Re:Execution Units Are Often Pipelined by dahart on Monday December 30, 2024 @08:27PM (#42555473)

Depends on what you mean by ‘cheaper’. Multiplies are still more gates. The adds are slower due to longer dependency chains, not because they cost more gates.

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