The Old New Thing

Creating double-precision integer multiplication with a quad-precision result from single-precision multiplication with a double-precision result

December 8, 2014 Dec 8, 2014 12/8/14

Raymond Chen

Suppose you want to multiply two double-word values producing a quad-word result, but your processor supports only single-word multiplication with a double-word result. For concreteness, let's say that your processor supports 32 × 32 → 64 multiplication and you want to implement 64 × 64 → 128 multiplication. (Sound like any processor you...