diff options
Diffstat (limited to 'compiler/cmm/CmmOpt.hs')
| -rw-r--r-- | compiler/cmm/CmmOpt.hs | 24 |
1 files changed, 6 insertions, 18 deletions
diff --git a/compiler/cmm/CmmOpt.hs b/compiler/cmm/CmmOpt.hs index 84499b97de..7c634c2201 100644 --- a/compiler/cmm/CmmOpt.hs +++ b/compiler/cmm/CmmOpt.hs @@ -21,7 +21,6 @@ import CmmUtils import Cmm import DynFlags -import FastTypes import Outputable import Platform @@ -376,30 +375,19 @@ cmmMachOpFoldM _ _ _ = Nothing -- 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. --- --- Used to be in MachInstrs --SDM. --- ToDo: remove use of unboxery --SDM. - --- Unboxery removed in favor of FastInt; but is the function supposed to fail --- on inputs >= 2147483648, or was that just an implementation artifact? --- And is this speed-critical, or can we just use Integer operations --- (including Data.Bits)? --- --Isaac Dupree exactLog2 :: Integer -> Maybe Integer -exactLog2 x_ - = if (x_ <= 0 || x_ >= 2147483648) then +exactLog2 x + = if (x <= 0 || x >= 2147483648) then Nothing else - case iUnbox (fromInteger x_) of { x -> - if (x `bitAndFastInt` negateFastInt x) /=# x then + if (x .&. (-x)) /= x then Nothing else - Just (toInteger (iBox (pow2 x))) - } + Just (pow2 x) where - pow2 x | x ==# _ILIT(1) = _ILIT(0) - | otherwise = _ILIT(1) +# pow2 (x `shiftR_FastInt` _ILIT(1)) + pow2 x | x == 1 = 0 + | otherwise = 1 + pow2 (x `shiftR` 1) -- ----------------------------------------------------------------------------- -- Utils |