    -- | Formats on this architecture
    --      A Format is a combination of width and class
    --
    --      TODO:   Signed vs unsigned?
    --
    --      TODO:   This module is currenly shared by all architectures because
    --              NCGMonad need to know about it to make a VReg. It would be better
    --              to have architecture specific formats, and do the overloading
    --              properly. eg SPARC doesn't care about FF80.
    --
    module Format (
        Format(..),
        intFormat,
        floatFormat,
        isFloatFormat,
        cmmTypeFormat,
        formatToWidth,
        formatInBytes
    )

    where

    import Cmm
    import Outputable

    -- It looks very like the old MachRep, but it's now of purely local
    -- significance, here in the native code generator.  You can change it
    -- without global consequences.
    --
    -- A major use is as an opcode qualifier; thus the opcode
    --      mov.l a b
    -- might be encoded
    --      MOV II32 a b
    -- where the Format field encodes the ".l" part.

    -- ToDo: it's not clear to me that we need separate signed-vs-unsigned formats
    --        here.  I've removed them from the x86 version, we'll see what happens --SDM

    -- ToDo: quite a few occurrences of Format could usefully be replaced by Width

    data Format
            = II8
            | II16
            | II32
            | II64
            | FF32
            | FF64
            | FF80
            deriving (Show, Eq)

    -- | Get the integer format of this width.
    intFormat :: Width -> Format
    intFormat width
     = case width of
            W8      -> II8
            W16     -> II16
            W32     -> II32
            W64     -> II64
            other   -> sorry $ "The native code generator cannot " ++
                "produce code for Format.intFormat " ++ show other
                ++ "\n\tConsider using the llvm backend with -fllvm"

    -- | Get the float format of this width.
    floatFormat :: Width -> Format
    floatFormat width
     = case width of
            W32     -> FF32
            W64     -> FF64
            other   -> pprPanic "Format.floatFormat" (ppr other)

    -- | Check if a format represents a floating point value.
    isFloatFormat :: Format -> Bool
    isFloatFormat format
     = case format of
            FF32    -> True
            FF64    -> True
            FF80    -> True
            _       -> False

    -- | Convert a Cmm type to a Format.
    cmmTypeFormat :: CmmType -> Format
    cmmTypeFormat ty
            | isFloatType ty        = floatFormat (typeWidth ty)
            | otherwise             = intFormat (typeWidth ty)

    -- | Get the Width of a Format.
    formatToWidth :: Format -> Width
    formatToWidth format
     = case format of
            II8             -> W8
            II16            -> W16
            II32            -> W32
            II64            -> W64
            FF32            -> W32
            FF64            -> W64
            FF80            -> W80

    formatInBytes :: Format -> Int
    formatInBytes = widthInBytes . formatToWidth