I was needing an (very) efficient way to rotate a byte a variable number
of positions when the following popped on my mind:


        btfsc    TABLAT, 2, ACCESS
        swapf    PRODL, F, ACCESS
        btfsc    TABLAT, 1, ACCESS
        rrncf    PRODL, F, ACCESS
        btfsc    TABLAT, 1, ACCESS
        rrncf    PRODL, F, ACCESS
        btfsc    TABLAT, 0, ACCESS
        rrncf    PRODL, F, ACCESS


The number of positions to rotate is in TABLAT and the value to be
rotated is in PRODL.
The routine can rotate from zero to 7 positions, takes only 8
instructions and as a bonus it is isochronous.

Did somebody already know it or can I boast that I invented it?


Isaac

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