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WIP: bitscan reverse

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Koichi Nakamura 2021-05-05 23:09:48 +09:00
parent d07e23eb00
commit 4f0380dafa
1 changed files with 27 additions and 1 deletions
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28
lib/bitscan.fs
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@ -37,12 +37,29 @@ create bsf-modulo-131-table
cells bsf-modulo-131-table + @ cells bsf-modulo-131-table + @
; export ; export
create msb-index-table
create msb-table
-1 , 0 , 1 , 1 , 2 , 2 , 2 , 2 , 3 , 3 , 3 , 3 , 3 , 3 , 3 , 3 ,
4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 , 4 ,
5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 ,
5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 , 5 ,
6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ,
6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ,
6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ,
6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 ,
\ Find the index of the most significant 1 bit \ Find the index of the most significant 1 bit
\ If u == 0, returns -1 \ If u == 0, returns -1
: bitscan-reverse ( u -- u ) : bitscan-reverse ( u -- u )
dup 0xff u< if cells msb-table + @ exit then
; export ; export
}private }private
@ -56,3 +73,12 @@ T{ 5 bitscan-forward -> 0 }T
T{ -1 bitscan-forward -> 0 }T T{ -1 bitscan-forward -> 0 }T
T{ max-int bitscan-forward -> 0 }T T{ max-int bitscan-forward -> 0 }T
T{ min-int bitscan-forward -> cell 8 * 1- }T T{ min-int bitscan-forward -> cell 8 * 1- }T
T{ 0 bitscan-reverse -> -1 }T
T{ 1 bitscan-reverse -> 0 }T
T{ 2 bitscan-reverse -> 1 }T
T{ 3 bitscan-reverse -> 1 }T
T{ 4 bitscan-reverse -> 2 }T
T{ -1 bitscan-reverse -> cell 8 * 1- }T
T{ max-int bitscan-reverse -> cell 8 * 2 - }T
T{ min-int bitscan-reverse -> cell 8 * 1- }T