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-- | Free regs map for i386 and x86_64
module RegAlloc.Linear.X86.FreeRegs
where
import X86.Regs
import RegClass
import Reg
import Data.Word
import Data.Bits
import Data.List
type FreeRegs
= Word32
noFreeRegs :: FreeRegs
noFreeRegs = 0
releaseReg :: RegNo -> FreeRegs -> FreeRegs
releaseReg n f = f .|. (1 `shiftL` n)
initFreeRegs :: FreeRegs
initFreeRegs = foldr releaseReg noFreeRegs allocatableRegs
getFreeRegs :: RegClass -> FreeRegs -> [RegNo] -- lazilly
getFreeRegs cls f = go f 0
where go 0 _ = []
go n m
| n .&. 1 /= 0 && regClass (regSingle m) == cls
= m : (go (n `shiftR` 1) $! (m+1))
| otherwise
= go (n `shiftR` 1) $! (m+1)
-- ToDo: there's no point looking through all the integer registers
-- in order to find a floating-point one.
allocateReg :: RegNo -> FreeRegs -> FreeRegs
allocateReg r f = f .&. complement (1 `shiftL` fromIntegral r)
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