Re: Switch statement code generation

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
(snip, someone wrote)


> [On machines with condition codes, I've seen binary searches expanded
> into code with compare and branch instructions; after the comparison
> you can do a three way branch on less, equal, or greater. -John]


I once saw in a Fortran book the suggestion that one use arithmetic
IF in place of computed GOTO with three labels.


            IF(N-2) 1,2,3


instead of


            GOTO (1,2,3),N


For modern processors depending on branch prediction logic,
either a branch table or address table will likely foil any
prediction system. Complicated conditional branching is likely
faster in that case.


-- glen
[Hey, it worked great on the 709. -John]

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