mirrors/Nim
1
0
Fork 0
mirror of https://github.com/nim-lang/Nim.git synced 2025-12-28 17:04:41 +00:00
Code Issues Packages Projects Releases Wiki Activity

Generate populationCount const at compile time (#7583)

Browse Source
This commit is contained in:
Oscar Nihlgård
2018-04-16 21:52:27 +02:00
committed by Andreas Rumpf
parent 38b2596ff9
commit c4d7cc3da0
1 changed files with 19 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
compiler/bitsets.nim
View File

@@ -72,24 +72,25 @@ proc bitSetContains(x, y: TBitSet): bool =
result = true
# Number of set bits for all values of int8
const populationCount: array[low(int8)..high(int8), int8] = [
1.int8, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7
]
const populationCount: array[low(int8)..high(int8), int8] = block:
var arr: array[low(int8)..high(int8), int8]
proc countSetBits(x: int8): int8 =
return
( x and 0b00000001'i8) +
((x and 0b00000010'i8) shr 1) +
((x and 0b00000100'i8) shr 2) +
((x and 0b00001000'i8) shr 3) +
((x and 0b00010000'i8) shr 4) +
((x and 0b00100000'i8) shr 5) +
((x and 0b01000000'i8) shr 6) +
((x and 0b10000000'i8) shr 7)
for it in low(int8)..high(int8):
arr[it] = countSetBits(it)
arr
proc bitSetCard(x: TBitSet): BiggestInt =
for it in x: