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-- | Free regs map for i386
module RegAlloc.Linear.X86.FreeRegs
where
import X86.Regs
import RegClass
import Reg
import Panic
import Platform
import Data.Word
import Data.Bits
import Data.Foldable (foldl')
newtype FreeRegs = FreeRegs Word32
deriving Show
noFreeRegs :: FreeRegs
noFreeRegs = FreeRegs 0
releaseReg :: RealReg -> FreeRegs -> FreeRegs
releaseReg (RealRegSingle n) (FreeRegs f)
= FreeRegs (f .|. (1 `shiftL` n))
releaseReg _ _
= panic "RegAlloc.Linear.X86.FreeRegs.releaseReg: no reg"
initFreeRegs :: Platform -> FreeRegs
initFreeRegs platform
= foldl' (flip releaseReg) noFreeRegs (allocatableRegs platform)
getFreeRegs :: Platform -> RegClass -> FreeRegs -> [RealReg] -- lazily
getFreeRegs platform cls (FreeRegs f) = go f 0
where go 0 _ = []
go n m
| n .&. 1 /= 0 && classOfRealReg platform (RealRegSingle m) == cls
= RealRegSingle 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 :: RealReg -> FreeRegs -> FreeRegs
allocateReg (RealRegSingle r) (FreeRegs f)
= FreeRegs (f .&. complement (1 `shiftL` r))
allocateReg _ _
= panic "RegAlloc.Linear.X86.FreeRegs.allocateReg: no reg"
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