diff options
| -rw-r--r-- | compiler/utils/Util.hs | 22 |
1 files changed, 8 insertions, 14 deletions
diff --git a/compiler/utils/Util.hs b/compiler/utils/Util.hs index dba5a4495f..ecbef752f1 100644 --- a/compiler/utils/Util.hs +++ b/compiler/utils/Util.hs @@ -1123,22 +1123,16 @@ toArgs str ----------------------------------------------------------------------------- -- Integers --- This algorithm for determining the $\log_2$ of exact powers of 2 comes --- from GCC. It requires bit manipulation primitives, and we use GHC --- extensions. Tough. - +-- | Determine the $\log_2$ of exact powers of 2 exactLog2 :: Integer -> Maybe Integer exactLog2 x - = if (x <= 0 || x >= 2147483648) then - Nothing - else - if (x .&. (-x)) /= x then - Nothing - else - Just (pow2 x) - where - pow2 x | x == 1 = 0 - | otherwise = 1 + pow2 (x `shiftR` 1) + | x <= 0 = Nothing + | x > fromIntegral (maxBound :: Int32) = Nothing + | x' .&. (-x') /= x' = Nothing + | otherwise = Just (fromIntegral c) + where + x' = fromIntegral x :: Int32 + c = countTrailingZeros x' {- -- ----------------------------------------------------------------------------- |