Author: Bruce Moreland
Date: 09:14:15 02/05/98
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On February 05, 1998 at 10:41:20, Robert Hyatt wrote: >On February 05, 1998 at 09:10:20, Amir Ban wrote: > >>On February 04, 1998 at 23:03:26, Bruce Moreland wrote: >> >>>Actually, it's a good idea to compile your program once and produce an >>>assembly listing ("-Fc" works great in MSVC), and search for "mul" and >>>"div", in an effort to minimize these. >>I thought modern processors do these rather fast. It still takes a few clocks, especially div. I can't remember if it also stalls the second pipe, but that would be bad, too. >you can't do better than AND/OR/XOR/SHIFT... on the machines I use, >those are >one-cycle jobbies... The shift instructions are actually pretty bad on the Pentium, they stall the second pipe, and maybe they even take more than one clock, I don't remember. "shl ax, 1" and "add ax, ax" are not equivalent, in terms of performance. The add instruction is always better. bruce
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