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[backport] fix #12395 (#12590)

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'countBits32' is now fixed in the same way that
'countBits64' was already patched earlier (by adding 'u32
where needed).
This commit is contained in:
Miran
2019-11-04 15:02:36 +01:00
committed by GitHub
parent 992f0a7756
commit ae32d637f7
1 changed files with 3 additions and 3 deletions
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6
lib/system/sets.nim
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@@ -17,9 +17,9 @@ type
proc countBits32(n: uint32): int {.compilerproc.} =
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
var v = uint32(n)
v = v - ((v shr 1) and 0x55555555)
v = (v and 0x33333333) + ((v shr 2) and 0x33333333)
result = (((v + (v shr 4) and 0xF0F0F0F) * 0x1010101) shr 24).int
v = v - ((v shr 1'u32) and 0x55555555'u32)
v = (v and 0x33333333'u32) + ((v shr 2'u32) and 0x33333333'u32)
result = (((v + (v shr 4'u32) and 0xF0F0F0F'u32) * 0x1010101) shr 24'u32).int
proc countBits64(n: uint64): int {.compilerproc, inline.} =
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel