{- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1998 \section[Literal]{@Literal@: literals} -} {-# LANGUAGE CPP, DeriveDataTypeable, ScopedTypeVariables #-} module Literal ( -- * Main data type Literal(..) -- Exported to ParseIface , LitNumType(..) -- ** Creating Literals , mkLitInt, mkLitIntWrap, mkLitIntWrapC , mkLitWord, mkLitWordWrap, mkLitWordWrapC , mkLitInt64, mkLitInt64Wrap , mkLitWord64, mkLitWord64Wrap , mkLitFloat, mkLitDouble , mkLitChar, mkLitString , mkLitInteger, mkLitNatural , mkLitNumber, mkLitNumberWrap -- ** Operations on Literals , literalType , absentLiteralOf , pprLiteral , litNumIsSigned , litNumCheckRange -- ** Predicates on Literals and their contents , litIsDupable, litIsTrivial, litIsLifted , inIntRange, inWordRange, tARGET_MAX_INT, inCharRange , isZeroLit , litFitsInChar , litValue, isLitValue, isLitValue_maybe, mapLitValue -- ** Coercions , word2IntLit, int2WordLit , narrowLit , narrow8IntLit, narrow16IntLit, narrow32IntLit , narrow8WordLit, narrow16WordLit, narrow32WordLit , char2IntLit, int2CharLit , float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit , nullAddrLit, rubbishLit, float2DoubleLit, double2FloatLit ) where #include "HsVersions.h" import GhcPrelude import TysPrim import PrelNames import Type import TyCon import Outputable import FastString import BasicTypes import Binary import Constants import DynFlags import GHC.Platform import UniqFM import Util import Data.ByteString (ByteString) import Data.Int import Data.Word import Data.Char import Data.Maybe ( isJust ) import Data.Data ( Data ) import Data.Proxy import Numeric ( fromRat ) {- ************************************************************************ * * \subsection{Literals} * * ************************************************************************ -} -- | So-called 'Literal's 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 -- data Literal = 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. -- See Note [Types of LitNumbers] below for the -- Type field. | 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 deriving Data -- | Numeric literal type data LitNumType = 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 deriving (Data,Enum,Eq,Ord) -- | Indicate if a numeric literal type supports negative numbers litNumIsSigned :: LitNumType -> Bool litNumIsSigned nt = case nt of LitNumInteger -> True LitNumNatural -> False LitNumInt -> True LitNumInt64 -> True LitNumWord -> False LitNumWord64 -> False {- Note [Integer literals] ~~~~~~~~~~~~~~~~~~~~~~~ An Integer literal is represented using, well, an Integer, to make it easier to write RULEs for them. They also contain the Integer type, so that e.g. literalType can return the right Type for them. They only get converted into real Core, mkInteger [c1, c2, .., cn] during the CorePrep phase, although TidyPgm looks ahead at what the core will be, so that it can see whether it involves CAFs. When we initally build an Integer literal, notably when deserialising it from an interface file (see the Binary instance below), we don't have convenient access to the mkInteger Id. So we just use an error thunk, and fill in the real Id when we do tcIfaceLit in TcIface. Note [Natural literals] ~~~~~~~~~~~~~~~~~~~~~~~ Similar to Integer literals. Note [String literals] ~~~~~~~~~~~~~~~~~~~~~~ String literals are UTF-8 encoded and stored into ByteStrings in the following ASTs: Haskell, Core, Stg, Cmm. TH can also emit ByteString based string literals with the BytesPrimL constructor (see #14741). It wasn't true before as [Word8] was used in Cmm AST and in TH which was quite bad for performance with large strings (see #16198 and #14741). To include string literals into output objects, the assembler code generator has to embed the UTF-8 encoded binary blob. See Note [Embedding large binary blobs] for more details. -} instance Binary LitNumType where put_ bh numTyp = putByte bh (fromIntegral (fromEnum numTyp)) get bh = do h <- getByte bh return (toEnum (fromIntegral h)) instance Binary Literal where put_ bh (LitChar aa) = do putByte bh 0; put_ bh aa put_ bh (LitString ab) = do putByte bh 1; put_ bh ab put_ bh (LitNullAddr) = do putByte bh 2 put_ bh (LitFloat ah) = do putByte bh 3; put_ bh ah put_ bh (LitDouble ai) = do putByte bh 4; put_ bh ai put_ bh (LitLabel aj mb fod) = do putByte bh 5 put_ bh aj put_ bh mb put_ bh fod put_ bh (LitNumber nt i _) = do putByte bh 6 put_ bh nt put_ bh i put_ bh (LitRubbish) = do putByte bh 7 get bh = do h <- getByte bh case h of 0 -> do aa <- get bh return (LitChar aa) 1 -> do ab <- get bh return (LitString ab) 2 -> do return (LitNullAddr) 3 -> do ah <- get bh return (LitFloat ah) 4 -> do ai <- get bh return (LitDouble ai) 5 -> do aj <- get bh mb <- get bh fod <- get bh return (LitLabel aj mb fod) 6 -> do nt <- get bh i <- get bh -- Note [Types of LitNumbers] let t = case nt of LitNumInt -> intPrimTy LitNumInt64 -> int64PrimTy LitNumWord -> wordPrimTy LitNumWord64 -> word64PrimTy -- See Note [Integer literals] LitNumInteger -> panic "Evaluated the place holder for mkInteger" -- and Note [Natural literals] LitNumNatural -> panic "Evaluated the place holder for mkNatural" return (LitNumber nt i t) _ -> do return (LitRubbish) instance Outputable Literal where ppr = pprLiteral id instance Eq Literal where a == b = compare a b == EQ -- | Needed for the @Ord@ instance of 'AltCon', which in turn is needed in -- 'TrieMap.CoreMap'. instance Ord Literal where compare = cmpLit {- Construction ~~~~~~~~~~~~ -} {- Note [Word/Int underflow/overflow] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ According to the Haskell Report 2010 (Sections 18.1 and 23.1 about signed and unsigned integral types): "All arithmetic is performed modulo 2^n, where n is the number of bits in the type." GHC stores Word# and Int# constant values as Integer. Core optimizations such as constant folding must ensure that the Integer value remains in the valid target Word/Int range (see #13172). The following functions are used to ensure this. Note that we *don't* warn the user about overflow. It's not done at runtime either, and compilation of completely harmless things like ((124076834 :: Word32) + (2147483647 :: Word32)) doesn't yield a warning. Instead we simply squash the value into the *target* Int/Word range. -} -- | Wrap a literal number according to its type wrapLitNumber :: DynFlags -> Literal -> Literal wrapLitNumber dflags v@(LitNumber nt i t) = case nt of LitNumInt -> case platformWordSize (targetPlatform dflags) of PW4 -> LitNumber nt (toInteger (fromIntegral i :: Int32)) t PW8 -> LitNumber nt (toInteger (fromIntegral i :: Int64)) t LitNumWord -> case platformWordSize (targetPlatform dflags) of PW4 -> LitNumber nt (toInteger (fromIntegral i :: Word32)) t PW8 -> LitNumber nt (toInteger (fromIntegral i :: Word64)) t LitNumInt64 -> LitNumber nt (toInteger (fromIntegral i :: Int64)) t LitNumWord64 -> LitNumber nt (toInteger (fromIntegral i :: Word64)) t LitNumInteger -> v LitNumNatural -> v wrapLitNumber _ x = x -- | Create a numeric 'Literal' of the given type mkLitNumberWrap :: DynFlags -> LitNumType -> Integer -> Type -> Literal mkLitNumberWrap dflags nt i t = wrapLitNumber dflags (LitNumber nt i t) -- | Check that a given number is in the range of a numeric literal litNumCheckRange :: DynFlags -> LitNumType -> Integer -> Bool litNumCheckRange dflags nt i = case nt of LitNumInt -> inIntRange dflags i LitNumWord -> inWordRange dflags i LitNumInt64 -> inInt64Range i LitNumWord64 -> inWord64Range i LitNumNatural -> i >= 0 LitNumInteger -> True -- | Create a numeric 'Literal' of the given type mkLitNumber :: DynFlags -> LitNumType -> Integer -> Type -> Literal mkLitNumber dflags nt i t = ASSERT2(litNumCheckRange dflags nt i, integer i) (LitNumber nt i t) -- | Creates a 'Literal' of type @Int#@ mkLitInt :: DynFlags -> Integer -> Literal mkLitInt dflags x = ASSERT2( inIntRange dflags x, integer x ) (mkLitIntUnchecked x) -- | Creates a 'Literal' of type @Int#@. -- If the argument is out of the (target-dependent) range, it is wrapped. -- See Note [Word/Int underflow/overflow] mkLitIntWrap :: DynFlags -> Integer -> Literal mkLitIntWrap dflags i = wrapLitNumber dflags $ mkLitIntUnchecked i -- | Creates a 'Literal' of type @Int#@ without checking its range. mkLitIntUnchecked :: Integer -> Literal mkLitIntUnchecked i = LitNumber LitNumInt i intPrimTy -- | Creates a 'Literal' of type @Int#@, as well as a 'Bool'ean 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 [Word/Int underflow/overflow] mkLitIntWrapC :: DynFlags -> Integer -> (Literal, Bool) mkLitIntWrapC dflags i = (n, i /= i') where n@(LitNumber _ i' _) = mkLitIntWrap dflags i -- | Creates a 'Literal' of type @Word#@ mkLitWord :: DynFlags -> Integer -> Literal mkLitWord dflags x = ASSERT2( inWordRange dflags x, integer x ) (mkLitWordUnchecked x) -- | Creates a 'Literal' of type @Word#@. -- If the argument is out of the (target-dependent) range, it is wrapped. -- See Note [Word/Int underflow/overflow] mkLitWordWrap :: DynFlags -> Integer -> Literal mkLitWordWrap dflags i = wrapLitNumber dflags $ mkLitWordUnchecked i -- | Creates a 'Literal' of type @Word#@ without checking its range. mkLitWordUnchecked :: Integer -> Literal mkLitWordUnchecked i = LitNumber LitNumWord i wordPrimTy -- | Creates a 'Literal' of type @Word#@, as well as a 'Bool'ean 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 [Word/Int underflow/overflow] mkLitWordWrapC :: DynFlags -> Integer -> (Literal, Bool) mkLitWordWrapC dflags i = (n, i /= i') where n@(LitNumber _ i' _) = mkLitWordWrap dflags i -- | Creates a 'Literal' of type @Int64#@ mkLitInt64 :: Integer -> Literal mkLitInt64 x = ASSERT2( inInt64Range x, integer x ) (mkLitInt64Unchecked x) -- | Creates a 'Literal' of type @Int64#@. -- If the argument is out of the range, it is wrapped. mkLitInt64Wrap :: DynFlags -> Integer -> Literal mkLitInt64Wrap dflags i = wrapLitNumber dflags $ mkLitInt64Unchecked i -- | Creates a 'Literal' of type @Int64#@ without checking its range. mkLitInt64Unchecked :: Integer -> Literal mkLitInt64Unchecked i = LitNumber LitNumInt64 i int64PrimTy -- | Creates a 'Literal' of type @Word64#@ mkLitWord64 :: Integer -> Literal mkLitWord64 x = ASSERT2( inWord64Range x, integer x ) (mkLitWord64Unchecked x) -- | Creates a 'Literal' of type @Word64#@. -- If the argument is out of the range, it is wrapped. mkLitWord64Wrap :: DynFlags -> Integer -> Literal mkLitWord64Wrap dflags i = wrapLitNumber dflags $ mkLitWord64Unchecked i -- | Creates a 'Literal' of type @Word64#@ without checking its range. mkLitWord64Unchecked :: Integer -> Literal mkLitWord64Unchecked i = LitNumber LitNumWord64 i word64PrimTy -- | Creates a 'Literal' of type @Float#@ mkLitFloat :: Rational -> Literal mkLitFloat = LitFloat -- | Creates a 'Literal' of type @Double#@ mkLitDouble :: Rational -> Literal mkLitDouble = LitDouble -- | Creates a 'Literal' of type @Char#@ mkLitChar :: Char -> Literal mkLitChar = LitChar -- | 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@ mkLitString :: String -> Literal -- stored UTF-8 encoded mkLitString s = LitString (bytesFS $ mkFastString s) mkLitInteger :: Integer -> Type -> Literal mkLitInteger x ty = LitNumber LitNumInteger x ty mkLitNatural :: Integer -> Type -> Literal mkLitNatural x ty = ASSERT2( inNaturalRange x, integer x ) (LitNumber LitNumNatural x ty) inIntRange, inWordRange :: DynFlags -> Integer -> Bool inIntRange dflags x = x >= tARGET_MIN_INT dflags && x <= tARGET_MAX_INT dflags inWordRange dflags x = x >= 0 && x <= tARGET_MAX_WORD dflags inNaturalRange :: Integer -> Bool inNaturalRange x = x >= 0 inInt64Range, inWord64Range :: Integer -> Bool inInt64Range x = x >= toInteger (minBound :: Int64) && x <= toInteger (maxBound :: Int64) inWord64Range x = x >= toInteger (minBound :: Word64) && x <= toInteger (maxBound :: Word64) inCharRange :: Char -> Bool inCharRange c = c >= '\0' && c <= chr tARGET_MAX_CHAR -- | Tests whether the literal represents a zero of whatever type it is isZeroLit :: Literal -> Bool isZeroLit (LitNumber _ 0 _) = True isZeroLit (LitFloat 0) = True isZeroLit (LitDouble 0) = True isZeroLit _ = False -- | Returns the 'Integer' contained in the 'Literal', for when that makes -- sense, i.e. for 'Char', 'Int', 'Word', 'LitInteger' and 'LitNatural'. litValue :: Literal -> Integer litValue l = case isLitValue_maybe l of Just x -> x Nothing -> pprPanic "litValue" (ppr l) -- | Returns the 'Integer' contained in the 'Literal', for when that makes -- sense, i.e. for 'Char' and numbers. isLitValue_maybe :: Literal -> Maybe Integer isLitValue_maybe (LitChar c) = Just $ toInteger $ ord c isLitValue_maybe (LitNumber _ i _) = Just i isLitValue_maybe _ = Nothing -- | 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 [Word/Int underflow/overflow] mapLitValue :: DynFlags -> (Integer -> Integer) -> Literal -> Literal mapLitValue _ f (LitChar c) = mkLitChar (fchar c) where fchar = chr . fromInteger . f . toInteger . ord mapLitValue dflags f (LitNumber nt i t) = wrapLitNumber dflags (LitNumber nt (f i) t) mapLitValue _ _ l = pprPanic "mapLitValue" (ppr l) -- | Indicate if the `Literal` contains an 'Integer' value, e.g. 'Char', -- 'Int', 'Word', 'LitInteger' and 'LitNatural'. isLitValue :: Literal -> Bool isLitValue = isJust . isLitValue_maybe {- Coercions ~~~~~~~~~ -} narrow8IntLit, narrow16IntLit, narrow32IntLit, narrow8WordLit, narrow16WordLit, narrow32WordLit, char2IntLit, int2CharLit, float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit, float2DoubleLit, double2FloatLit :: Literal -> Literal word2IntLit, int2WordLit :: DynFlags -> Literal -> Literal word2IntLit dflags (LitNumber LitNumWord w _) -- Map Word range [max_int+1, max_word] -- to Int range [min_int , -1] -- Range [0,max_int] has the same representation with both Int and Word | w > tARGET_MAX_INT dflags = mkLitInt dflags (w - tARGET_MAX_WORD dflags - 1) | otherwise = mkLitInt dflags w word2IntLit _ l = pprPanic "word2IntLit" (ppr l) int2WordLit dflags (LitNumber LitNumInt i _) -- Map Int range [min_int , -1] -- to Word range [max_int+1, max_word] -- Range [0,max_int] has the same representation with both Int and Word | i < 0 = mkLitWord dflags (1 + tARGET_MAX_WORD dflags + i) | otherwise = mkLitWord dflags i int2WordLit _ l = pprPanic "int2WordLit" (ppr l) -- | Narrow a literal number (unchecked result range) narrowLit :: forall a. Integral a => Proxy a -> Literal -> Literal narrowLit _ (LitNumber nt i t) = LitNumber nt (toInteger (fromInteger i :: a)) t narrowLit _ l = pprPanic "narrowLit" (ppr l) narrow8IntLit = narrowLit (Proxy :: Proxy Int8) narrow16IntLit = narrowLit (Proxy :: Proxy Int16) narrow32IntLit = narrowLit (Proxy :: Proxy Int32) narrow8WordLit = narrowLit (Proxy :: Proxy Word8) narrow16WordLit = narrowLit (Proxy :: Proxy Word16) narrow32WordLit = narrowLit (Proxy :: Proxy Word32) char2IntLit (LitChar c) = mkLitIntUnchecked (toInteger (ord c)) char2IntLit l = pprPanic "char2IntLit" (ppr l) int2CharLit (LitNumber _ i _) = LitChar (chr (fromInteger i)) int2CharLit l = pprPanic "int2CharLit" (ppr l) float2IntLit (LitFloat f) = mkLitIntUnchecked (truncate f) float2IntLit l = pprPanic "float2IntLit" (ppr l) int2FloatLit (LitNumber _ i _) = LitFloat (fromInteger i) int2FloatLit l = pprPanic "int2FloatLit" (ppr l) double2IntLit (LitDouble f) = mkLitIntUnchecked (truncate f) double2IntLit l = pprPanic "double2IntLit" (ppr l) int2DoubleLit (LitNumber _ i _) = LitDouble (fromInteger i) int2DoubleLit l = pprPanic "int2DoubleLit" (ppr l) float2DoubleLit (LitFloat f) = LitDouble f float2DoubleLit l = pprPanic "float2DoubleLit" (ppr l) double2FloatLit (LitDouble d) = LitFloat d double2FloatLit l = pprPanic "double2FloatLit" (ppr l) nullAddrLit :: Literal nullAddrLit = LitNullAddr -- | A nonsense literal of type @forall (a :: 'TYPE' 'UnliftedRep'). a@. rubbishLit :: Literal rubbishLit = LitRubbish {- Predicates ~~~~~~~~~~ -} -- | 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# -> 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# (indexInt8OffAddr# 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"# ("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. litIsTrivial :: Literal -> Bool -- c.f. CoreUtils.exprIsTrivial litIsTrivial (LitString _) = False litIsTrivial (LitNumber nt _ _) = case nt of LitNumInteger -> False LitNumNatural -> False LitNumInt -> True LitNumInt64 -> True LitNumWord -> True LitNumWord64 -> True litIsTrivial _ = True -- | True if code space does not go bad if we duplicate this literal litIsDupable :: DynFlags -> Literal -> Bool -- c.f. CoreUtils.exprIsDupable litIsDupable _ (LitString _) = False litIsDupable dflags (LitNumber nt i _) = case nt of LitNumInteger -> inIntRange dflags i LitNumNatural -> inIntRange dflags i LitNumInt -> True LitNumInt64 -> True LitNumWord -> True LitNumWord64 -> True litIsDupable _ _ = True litFitsInChar :: Literal -> Bool litFitsInChar (LitNumber _ i _) = i >= toInteger (ord minBound) && i <= toInteger (ord maxBound) litFitsInChar _ = False litIsLifted :: Literal -> Bool litIsLifted (LitNumber nt _ _) = case nt of LitNumInteger -> True LitNumNatural -> True LitNumInt -> False LitNumInt64 -> False LitNumWord -> False LitNumWord64 -> False litIsLifted _ = False {- Types ~~~~~ Note [Types of LitNumbers] ~~~~~~~~~~~~~~~~~~~~~~~~~~ A LitNumber's type is always known from its LitNumType: LitNumInteger -> Integer LitNumNatural -> Natural LitNumInt -> Int# (intPrimTy) LitNumInt64 -> Int64# (int64PrimTy) LitNumWord -> Word# (wordPrimTy) LitNumWord64 -> Word64# (word64PrimTy) The reason why we have a Type field is because Integer and Natural types live outside of GHC (in the libraries), so we have to get the actual Type via lookupTyCon, tcIfaceTyConByName etc. that's too inconvenient in the call sites of literalType, so we do that when creating these literals, and literalType simply reads the field. (But see also Note [Integer literals] and Note [Natural literals]) -} -- | Find the Haskell 'Type' the literal occupies literalType :: Literal -> Type literalType LitNullAddr = addrPrimTy literalType (LitChar _) = charPrimTy literalType (LitString _) = addrPrimTy literalType (LitFloat _) = floatPrimTy literalType (LitDouble _) = doublePrimTy literalType (LitLabel _ _ _) = addrPrimTy literalType (LitNumber _ _ t) = t -- Note [Types of LitNumbers] literalType (LitRubbish) = mkForAllTy a Inferred (mkTyVarTy a) where a = alphaTyVarUnliftedRep absentLiteralOf :: TyCon -> Maybe Literal -- Return a literal of the appropriate primitive -- TyCon, to use as a placeholder when it doesn't matter -- Rubbish literals are handled in WwLib, because -- 1. Looking at the TyCon is not enough, we need the actual type -- 2. This would need to return a type application to a literal absentLiteralOf tc = lookupUFM absent_lits (tyConName tc) absent_lits :: UniqFM Literal absent_lits = listToUFM [ (addrPrimTyConKey, LitNullAddr) , (charPrimTyConKey, LitChar 'x') , (intPrimTyConKey, mkLitIntUnchecked 0) , (int64PrimTyConKey, mkLitInt64Unchecked 0) , (wordPrimTyConKey, mkLitWordUnchecked 0) , (word64PrimTyConKey, mkLitWord64Unchecked 0) , (floatPrimTyConKey, LitFloat 0) , (doublePrimTyConKey, LitDouble 0) ] {- Comparison ~~~~~~~~~~ -} cmpLit :: Literal -> Literal -> Ordering cmpLit (LitChar a) (LitChar b) = a `compare` b cmpLit (LitString a) (LitString b) = a `compare` b cmpLit (LitNullAddr) (LitNullAddr) = EQ cmpLit (LitFloat a) (LitFloat b) = a `compare` b cmpLit (LitDouble a) (LitDouble b) = a `compare` b cmpLit (LitLabel a _ _) (LitLabel b _ _) = a `compare` b cmpLit (LitNumber nt1 a _) (LitNumber nt2 b _) | nt1 == nt2 = a `compare` b | otherwise = nt1 `compare` nt2 cmpLit (LitRubbish) (LitRubbish) = EQ cmpLit lit1 lit2 | litTag lit1 < litTag lit2 = LT | otherwise = GT litTag :: Literal -> Int litTag (LitChar _) = 1 litTag (LitString _) = 2 litTag (LitNullAddr) = 3 litTag (LitFloat _) = 4 litTag (LitDouble _) = 5 litTag (LitLabel _ _ _) = 6 litTag (LitNumber {}) = 7 litTag (LitRubbish) = 8 {- Printing ~~~~~~~~ * See Note [Printing of literals in Core] -} pprLiteral :: (SDoc -> SDoc) -> Literal -> SDoc pprLiteral _ (LitChar c) = pprPrimChar c pprLiteral _ (LitString s) = pprHsBytes s pprLiteral _ (LitNullAddr) = text "__NULL" pprLiteral _ (LitFloat f) = float (fromRat f) <> primFloatSuffix pprLiteral _ (LitDouble d) = double (fromRat d) <> primDoubleSuffix pprLiteral add_par (LitNumber nt i _) = case nt of LitNumInteger -> pprIntegerVal add_par i LitNumNatural -> pprIntegerVal add_par i LitNumInt -> pprPrimInt i LitNumInt64 -> pprPrimInt64 i LitNumWord -> pprPrimWord i LitNumWord64 -> pprPrimWord64 i pprLiteral add_par (LitLabel l mb fod) = add_par (text "__label" <+> b <+> ppr fod) where b = case mb of Nothing -> pprHsString l Just x -> doubleQuotes (text (unpackFS l ++ '@':show x)) pprLiteral _ (LitRubbish) = text "__RUBBISH" pprIntegerVal :: (SDoc -> SDoc) -> Integer -> SDoc -- See Note [Printing of literals in Core]. pprIntegerVal add_par i | i < 0 = add_par (integer i) | otherwise = integer i {- Note [Printing of literals in Core] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The function `add_par` is used to wrap parenthesis around negative integers (`LitInteger`) and labels (`LitLabel`), if they occur in a context requiring an atomic thing (for example function application). Although not all Core literals would be valid Haskell, we are trying to stay as close as possible to Haskell syntax in the printing of Core, to make it easier for a Haskell user to read Core. To that end: * We do print parenthesis around negative `LitInteger`, because we print `LitInteger` using plain number literals (no prefix or suffix), and plain number literals in Haskell require parenthesis in contexts like function application (i.e. `1 - -1` is not valid Haskell). * We don't print parenthesis around other (negative) literals, because they aren't needed in GHC/Haskell either (i.e. `1# -# -1#` is accepted by GHC's parser). Literal Output Output if context requires an atom (if different) ------- ------- ---------------------- LitChar 'a'# LitString "aaa"# LitNullAddr "__NULL" LitInt -1# LitInt64 -1L# LitWord 1## LitWord64 1L## LitFloat -1.0# LitDouble -1.0## LitInteger -1 (-1) LitLabel "__label" ... ("__label" ...) LitRubbish "__RUBBISH" Note [Rubbish literals] ~~~~~~~~~~~~~~~~~~~~~~~ During worker/wrapper after demand analysis, where an argument is unused (absent) we do the following w/w split (supposing that y is absent): f x y z = e ===> f x y z = $wf x z $wf x z = let y = <absent value> in e Usually the binding for y is ultimately optimised away, and even if not it should never be evaluated -- but that's the way the w/w split starts off. What is <absent value>? * For lifted values <absent value> can be a call to 'error'. * For primitive types like Int# or Word# we can use any random value of that type. * But what about /unlifted/ but /boxed/ types like MutVar# or Array#? We need a literal value of that type. That is 'LitRubbish'. Since we need a rubbish literal for many boxed, unlifted types, we say that LitRubbish has type LitRubbish :: forall (a :: TYPE UnliftedRep). a So we might see a w/w split like $wf x z = let y :: Array# Int = LitRubbish @(Array# Int) in e Recall that (TYPE UnliftedRep) is the kind of boxed, unlifted heap pointers. Here are the moving parts: * We define LitRubbish as a constructor in Literal.Literal * It is given its polymoprhic type by Literal.literalType * WwLib.mk_absent_let introduces a LitRubbish for absent arguments of boxed, unlifted type. * In CoreToSTG we convert (RubishLit @t) to just (). STG is untyped, so it doesn't matter that it points to a lifted value. The important thing is that it is a heap pointer, which the garbage collector can follow if it encounters it. We considered maintaining LitRubbish in STG, and lowering it in the code genreators, but it seems simpler to do it once and for all in CoreToSTG. In ByteCodeAsm we just lower it as a 0 literal, because it's all boxed and lifted to the host GC anyway. -}