|I like it. How 'bout:
|
|    rlf   test,W
|    andlw 0x0e
|    addwf pcl,f
|    bcf   PORTB,0
|    return
|    bcf   PORTB,1
|    return
|    .
|    .
|    .
|    bcf   PORTB,7
|    return
|
|7-iso cycles.

Nice.  If code space is a bit tight, an alternative would be...

MaskTbl:                ; Put this part in low 256 bytes
        andlw   7
        addwf   PC
        db      1,2,4,8,16,32,64,128

RoutineThatNeedsToClearBit:
        ...
        movf    BitNum,w
        call    MaskTbl
        xorlw   255
        andwf   PORTB,f

10 cycles as written; each of the following will save a cycle:

-1- If you have the table values complemented, you can eliminate the
    xorlw 255 instruction.  The table is written as it is to allow
    use in bit-setting or bit-toggling applications as well as bit-
    clearing ones.

-2- Skipping the andlw 7 at MaskTbl.  Of course, you'd better make
    sure your bit address is 0-7 if you do that.

-3- Starting with the bit number in W instead of a file register.

Thus, this version--while not as fast as the other one--uses less code
space.  Note that the table in this version may be used by many inst-
ances of the code below.  If there are several places in the program
where you need to selectively clear bits from different registers,
that could be a major asset.

Note also that this version requires one layer of stack depth; the
version posted previously does not [the 'returns' could be replaced
by 'goto's if desired].