Literal

Main data type

data Literal

So-called Literals are one of:

• An unboxed numeric literal or floating-point literal which is presumed to be surrounded by appropriate constructors (Int#, etc.), so that the overall thing makes sense.

We maintain the invariant that the Integer in the LitNumber constructor is actually in the (possibly target-dependent) range. The mkLit{Int,Word}*Wrap smart constructors ensure this by applying the target machine's wrapping semantics. Use these in situations where you know the wrapping semantics are correct.

• The literal derived from the label mentioned in a "foreign label" declaration (LitLabel)
• A LitRubbish to be used in place of values of UnliftedRep (i.e. 'MutVar#') when the the value is never used.
• A character
• A string
• The NULL pointer

Constructors

LitChar Char

Char# - at least 31 bits. Create with mkLitChar

LitNumber !LitNumType !Integer Type

Any numeric literal that can be internally represented with an Integer

LitString ByteString

A string-literal: stored and emitted UTF-8 encoded, we'll arrange to decode it at runtime. Also emitted with a '\0' terminator. Create with mkLitString

LitNullAddr

The NULL pointer, the only pointer value that can be represented as a Literal. Create with nullAddrLit

LitRubbish

A nonsense value, used when an unlifted binding is absent and has type forall (a :: TYPE UnliftedRep). a. May be lowered by code-gen to any possible value. Also see Note [Rubbish literals]

LitFloat Rational

Float#. Create with mkLitFloat

LitDouble Rational

Double#. Create with mkLitDouble

LitLabel FastString (Maybe Int) FunctionOrData

A label literal. Parameters:

1) The name of the symbol mentioned in the declaration

2) The size (in bytes) of the arguments the label expects. Only applicable with stdcall labels. Just x => <x> will be appended to label name when emitting assembly.

3) Flag indicating whether the symbol references a function or a data

Instances

Eq Literal

Defined in Literal

Methods

(==) :: Literal -> Literal -> Bool

(/=) :: Literal -> Literal -> Bool

Data Literal

Defined in Literal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Literal -> c Literal

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Literal

toConstr :: Literal -> Constr

dataTypeOf :: Literal -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Literal)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Literal)

gmapT :: (forall b. Data b => b -> b) -> Literal -> Literal

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Literal -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Literal -> r

gmapQ :: (forall d. Data d => d -> u) -> Literal -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Literal -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Literal -> m Literal

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Literal -> m Literal

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Literal -> m Literal

Ord Literal

Needed for the Ord instance of AltCon, which in turn is needed in CoreMap.

Defined in Literal

Methods

compare :: Literal -> Literal -> Ordering

(<) :: Literal -> Literal -> Bool

(<=) :: Literal -> Literal -> Bool

(>) :: Literal -> Literal -> Bool

(>=) :: Literal -> Literal -> Bool

max :: Literal -> Literal -> Literal

min :: Literal -> Literal -> Literal

Outputable Literal

Defined in Literal

Methods

ppr :: Literal -> SDoc

pprPrec :: Rational -> Literal -> SDoc

Binary Literal

Defined in Literal

Methods

put_ :: BinHandle -> Literal -> IO ()

put :: BinHandle -> Literal -> IO (Bin Literal)

get :: BinHandle -> IO Literal

data LitNumType

Numeric literal type

Constructors

LitNumInteger

Integer (see Note [Integer literals])

LitNumNatural

Natural (see Note [Natural literals])

LitNumInt

Int# - according to target machine

LitNumInt64

Int64# - exactly 64 bits

LitNumWord

Word# - according to target machine

LitNumWord64

Word64# - exactly 64 bits

Instances

Enum LitNumType

Defined in Literal

Methods

succ :: LitNumType -> LitNumType

pred :: LitNumType -> LitNumType

toEnum :: Int -> LitNumType

fromEnum :: LitNumType -> Int

enumFrom :: LitNumType -> [LitNumType]

enumFromThen :: LitNumType -> LitNumType -> [LitNumType]

enumFromTo :: LitNumType -> LitNumType -> [LitNumType]

enumFromThenTo :: LitNumType -> LitNumType -> LitNumType -> [LitNumType]

Eq LitNumType

Defined in Literal

Methods

(==) :: LitNumType -> LitNumType -> Bool

(/=) :: LitNumType -> LitNumType -> Bool

Data LitNumType

Defined in Literal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> LitNumType -> c LitNumType

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c LitNumType

toConstr :: LitNumType -> Constr

dataTypeOf :: LitNumType -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c LitNumType)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c LitNumType)

gmapT :: (forall b. Data b => b -> b) -> LitNumType -> LitNumType

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> LitNumType -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> LitNumType -> r

gmapQ :: (forall d. Data d => d -> u) -> LitNumType -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> LitNumType -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> LitNumType -> m LitNumType

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> LitNumType -> m LitNumType

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> LitNumType -> m LitNumType

Ord LitNumType

Defined in Literal

Methods

compare :: LitNumType -> LitNumType -> Ordering

(<) :: LitNumType -> LitNumType -> Bool

(<=) :: LitNumType -> LitNumType -> Bool

(>) :: LitNumType -> LitNumType -> Bool

(>=) :: LitNumType -> LitNumType -> Bool

max :: LitNumType -> LitNumType -> LitNumType

min :: LitNumType -> LitNumType -> LitNumType

Binary LitNumType

Defined in Literal

Methods

put_ :: BinHandle -> LitNumType -> IO ()

put :: BinHandle -> LitNumType -> IO (Bin LitNumType)

get :: BinHandle -> IO LitNumType

Creating Literals

mkLitInt :: DynFlags -> Integer -> Literal

Creates a Literal of type Int#

mkLitIntWrap :: DynFlags -> Integer -> Literal

Creates a Literal of type Int#. If the argument is out of the (target-dependent) range, it is wrapped. See Note [WordInt underflowoverflow]

mkLitIntWrapC :: DynFlags -> Integer -> (Literal, Bool)

Creates a Literal of type Int#, as well as a Boolean flag indicating overflow. That is, if the argument is out of the (target-dependent) range the argument is wrapped and the overflow flag will be set. See Note [WordInt underflowoverflow]

mkLitWord :: DynFlags -> Integer -> Literal

Creates a Literal of type Word#

mkLitWordWrap :: DynFlags -> Integer -> Literal

Creates a Literal of type Word#. If the argument is out of the (target-dependent) range, it is wrapped. See Note [WordInt underflowoverflow]

mkLitWordWrapC :: DynFlags -> Integer -> (Literal, Bool)

Creates a Literal of type Word#, as well as a Boolean flag indicating carry. That is, if the argument is out of the (target-dependent) range the argument is wrapped and the carry flag will be set. See Note [WordInt underflowoverflow]

mkLitInt64 :: Integer -> Literal

Creates a Literal of type Int64#

mkLitInt64Wrap :: DynFlags -> Integer -> Literal

Creates a Literal of type Int64#. If the argument is out of the range, it is wrapped.

mkLitWord64 :: Integer -> Literal

Creates a Literal of type Word64#

mkLitWord64Wrap :: DynFlags -> Integer -> Literal

Creates a Literal of type Word64#. If the argument is out of the range, it is wrapped.

mkLitFloat :: Rational -> Literal

Creates a Literal of type Float#

mkLitDouble :: Rational -> Literal

Creates a Literal of type Double#

mkLitChar :: Char -> Literal

Creates a Literal of type Char#

mkLitString :: String -> Literal

Creates a Literal of type Addr#, which is appropriate for passing to e.g. some of the "error" functions in GHC.Err such as GHC.Err.runtimeError

mkLitInteger :: Integer -> Type -> Literal

mkLitNatural :: Integer -> Type -> Literal

mkLitNumber :: DynFlags -> LitNumType -> Integer -> Type -> Literal

Create a numeric Literal of the given type

mkLitNumberWrap :: DynFlags -> LitNumType -> Integer -> Type -> Literal

Create a numeric Literal of the given type

Operations on Literals

literalType :: Literal -> Type

Find the Haskell Type the literal occupies

absentLiteralOf :: TyCon -> Maybe Literal

pprLiteral :: (SDoc -> SDoc) -> Literal -> SDoc

litNumIsSigned :: LitNumType -> Bool

Indicate if a numeric literal type supports negative numbers

litNumCheckRange :: DynFlags -> LitNumType -> Integer -> Bool

Check that a given number is in the range of a numeric literal

Predicates on Literals and their contents

litIsDupable :: DynFlags -> Literal -> Bool

True if code space does not go bad if we duplicate this literal

litIsTrivial :: Literal -> Bool

True if there is absolutely no penalty to duplicating the literal. False principally of strings.

"Why?", you say? I'm glad you asked. Well, for one duplicating strings would blow up code sizes. Not only this, it's also unsafe.

Consider a program that wants to traverse a string. One way it might do this is to first compute the Addr# pointing to the end of the string, and then, starting from the beginning, bump a pointer using eqAddr# to determine the end. For instance,

-- Given pointers to the start and end of a string, count how many zeros
-- the string contains.
countZeros :: Addr -> -> Int
countZeros start end = go start 0
  where
    go off n
      | off `addrEq#` end = n
      | otherwise         = go (off `plusAddr#` 1) n'
      where n' | isTrue off 0 0#) = n + 1
               | otherwise                                 = n

Consider what happens if we considered strings to be trivial (and therefore duplicable) and emitted a call like countZeros "hello" plusAddr# 5). The beginning and end pointers do not belong to the same string, meaning that an iteration like the above would blow up terribly. This is what happened in #12757.

Ultimately the solution here is to make primitive strings a bit more structured, ensuring that the compiler can't inline in ways that will break user code. One approach to this is described in #8472.

litIsLifted :: Literal -> Bool

inIntRange :: DynFlags -> Integer -> Bool

inWordRange :: DynFlags -> Integer -> Bool

tARGET_MAX_INT :: DynFlags -> Integer

inCharRange :: Char -> Bool

isZeroLit :: Literal -> Bool

Tests whether the literal represents a zero of whatever type it is

litFitsInChar :: Literal -> Bool

litValue :: Literal -> Integer

Returns the Integer contained in the Literal, for when that makes sense, i.e. for Char, Int, Word, LitInteger and LitNatural.

isLitValue :: Literal -> Bool

Indicate if the Literal contains an Integer value, e.g. Char, Int, Word, LitInteger and LitNatural.

isLitValue_maybe :: Literal -> Maybe Integer

Returns the Integer contained in the Literal, for when that makes sense, i.e. for Char and numbers.

mapLitValue :: DynFlags -> (Integer -> Integer) -> Literal -> Literal

Apply a function to the Integer contained in the Literal, for when that makes sense, e.g. for Char and numbers. For fixed-size integral literals, the result will be wrapped in accordance with the semantics of the target type. See Note [WordInt underflowoverflow]

Coercions

word2IntLit :: DynFlags -> Literal -> Literal

int2WordLit :: DynFlags -> Literal -> Literal

narrowLit :: forall a. Integral a => Proxy a -> Literal -> Literal

Narrow a literal number (unchecked result range)

narrow8IntLit :: Literal -> Literal

narrow16IntLit :: Literal -> Literal

narrow32IntLit :: Literal -> Literal

narrow8WordLit :: Literal -> Literal

narrow16WordLit :: Literal -> Literal

narrow32WordLit :: Literal -> Literal

char2IntLit :: Literal -> Literal

int2CharLit :: Literal -> Literal

float2IntLit :: Literal -> Literal

int2FloatLit :: Literal -> Literal

double2IntLit :: Literal -> Literal

int2DoubleLit :: Literal -> Literal

nullAddrLit :: Literal

rubbishLit :: Literal

A nonsense literal of type forall (a :: TYPE UnliftedRep). a.

float2DoubleLit :: Literal -> Literal

double2FloatLit :: Literal -> Literal