On Sun, 26 Aug 2018 18:32:29 +0200 Florian Klämpfl <flor...@freepascal.org> wrote:
> Am 26.08.2018 um 11:43 schrieb Giuliano Colla: > > Il 23/08/2018 11:34, Marco Borsari via fpc-pascal ha scritto: > > > >> It would be for the Wirth optimization in the access of an array, > >> when the index is 0 or 1, allowing the elimination of a multiplication. > > > > I'm afraid that this sort of optimization is rather outdated, and doesn't > > take into account a number of factors which > > make modern processors behave quite differently from old times ones. > > Multiplication is much less expensive then a jmp in most cases on today's > CPUs. > > It is even the other way round, it is often useful to replace an if statement > by a multiplication like: > > if a>b then > Inc(c,d); > > can be replaced on modern CPUs by > > Inc(c,d*ord(a>b)); Ah I see, anyway I did not think that, as Giuliano said, beacuse of alignment of array element, the multiplication is already substituded by a shift, and the essence of a branch table becomes superflous. Thank you for your time, Marco _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
