mirror of
https://github.com/nineties/planckforth
synced 2024-12-26 21:58:42 +01:00
56 lines
1.5 KiB
Forth
56 lines
1.5 KiB
Forth
\ planckforth -
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\ Copyright (C) 2021 nineties
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( === Bit-Scan operations === )
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cell 16 > [if]
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." Bit-Scan for integers longer than 128bits is not supported"
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not-supported
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[then]
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private{
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create bsf-modulo-131-table
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-1 , 0 , 1 , 72 , 2 , 46 , 73 , 96 ,
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3 , 14 , 47 , 56 , 74 , 18 , 97 , 118 ,
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4 , 43 , 15 , 35 , 48 , 38 , 57 , 23 ,
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75 , 92 , 19 , 86 , 98 , 51 , 119 , 29 ,
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5 , -1 , 44 , 12 , 16 , 41 , 36 , 90 ,
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49 , 126 , 39 , 124 , 58 , 60 , 24 , 105 ,
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76 , 62 , 93 , 115 , 20 , 26 , 87 , 102 ,
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99 , 107 , 52 , 82 , 120 , 78 , 30 , 110 ,
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6 , 64 , -1 , 71 , 45 , 95 , 13 , 55 ,
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17 , 117 , 42 , 34 , 37 , 22 , 91 , 85 ,
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50 , 28 , 127 , 11 , 40 , 89 , 125 , 123 ,
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59 , 104 , 61 , 114 , 25 , 101 , 106 , 81 ,
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77 , 109 , 63 , 70 , 94 , 54 , 116 , 33 ,
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21 , 84 , 27 , 10 , 88 , 122 , 103 , 113 ,
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100 , 80 , 108 , 69 , 53 , 32 , 83 , 9 ,
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121 , 112 , 79 , 68 , 31 , 8 , 111 , 67 ,
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7 , 66 , 65 ,
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\ Find the index of the least significant 1 bit
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\ If u == 0, returns -1
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: bitscan-forward ( u -- u )
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dup negate and 131 mod cells bsf-modulo-131-table + @
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; export
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create msb-index-table
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\ Find the index of the most significant 1 bit
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\ If u == 0, returns -1
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: bitscan-reverse ( u -- u )
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; export
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}private
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T{ 0 bitscan-forward -> -1 }T
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T{ 1 bitscan-forward -> 0 }T
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T{ 2 bitscan-forward -> 1 }T
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T{ 3 bitscan-forward -> 0 }T
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T{ 4 bitscan-forward -> 2 }T
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T{ 5 bitscan-forward -> 0 }T
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T{ -1 bitscan-forward -> 0 }T
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T{ max-int bitscan-forward -> 0 }T
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T{ min-int bitscan-forward -> cell 8 * 1- }T
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