/ghc-7.0.4/compiler/basicTypes/Literal.lhs

%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1998
%
\section[Literal]{@Literal@: Machine literals (unboxed, of course)}

\begin{code}
{-# OPTIONS -fno-warn-incomplete-patterns #-}
-- The above warning supression flag is a temporary kludge.
-- While working on this module you are encouraged to remove it and fix
-- any warnings in the module. See
--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
-- for details
{-# LANGUAGE DeriveDataTypeable #-}

module Literal
	( 
	-- * Main data type
	  Literal(..)		-- Exported to ParseIface
	
	-- ** Creating Literals
	, mkMachInt, mkMachWord
	, mkMachInt64, mkMachWord64
	, mkMachFloat, mkMachDouble
	, mkMachChar, mkMachString
	
	-- ** Operations on Literals
	, literalType
	, hashLiteral
        , absentLiteralOf

        -- ** Predicates on Literals and their contents
	, litIsDupable, litIsTrivial
	, inIntRange, inWordRange, tARGET_MAX_INT, inCharRange
	, isZeroLit
	, litFitsInChar

        -- ** Coercions
	, word2IntLit, int2WordLit
	, narrow8IntLit, narrow16IntLit, narrow32IntLit
	, narrow8WordLit, narrow16WordLit, narrow32WordLit
	, char2IntLit, int2CharLit
	, float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit
	, nullAddrLit, float2DoubleLit, double2FloatLit
	) where

import TysPrim
import PrelNames
import Type
import TyCon
import Outputable
import FastTypes
import FastString
import BasicTypes
import Binary
import Constants
import UniqFM
import Data.Int
import Data.Ratio
import Data.Word
import Data.Char
import Data.Data( Data, Typeable )
\end{code}


%************************************************************************
%*									*
\subsection{Literals}
%*									*
%************************************************************************

\begin{code}
-- | So-called 'Literal's are one of:
--
-- * An unboxed (/machine/) literal ('MachInt', 'MachFloat', etc.),
--   which is presumed to be surrounded by appropriate constructors
--   (@Int#@, etc.), so that the overall thing makes sense.
--
-- * The literal derived from the label mentioned in a \"foreign label\" 
--   declaration ('MachLabel')
data Literal
  =	------------------
	-- First the primitive guys
    MachChar	Char            -- ^ @Char#@ - at least 31 bits. Create with 'mkMachChar'

  | MachStr	FastString	-- ^ 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 'mkMachString'

  | MachNullAddr                -- ^ The @NULL@ pointer, the only pointer value
                                -- that can be represented as a Literal. Create 
                                -- with 'nullAddrLit'

  | MachInt	Integer		-- ^ @Int#@ - at least @WORD_SIZE_IN_BITS@ bits. Create with 'mkMachInt'
  | MachInt64	Integer		-- ^ @Int64#@ - at least 64 bits. Create with 'mkMachInt64'
  | MachWord	Integer		-- ^ @Word#@ - at least @WORD_SIZE_IN_BITS@ bits. Create with 'mkMachWord'
  | MachWord64	Integer		-- ^ @Word64#@ - at least 64 bits. Create with 'mkMachWord64'

  | MachFloat	Rational        -- ^ @Float#@. Create with 'mkMachFloat'
  | MachDouble	Rational        -- ^ @Double#@. Create with 'mkMachDouble'

  | MachLabel   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.
  deriving (Data, Typeable)
\end{code}

Binary instance

\begin{code}
instance Binary Literal where
    put_ bh (MachChar aa)     = do putByte bh 0; put_ bh aa
    put_ bh (MachStr ab)      = do putByte bh 1; put_ bh ab
    put_ bh (MachNullAddr)    = do putByte bh 2
    put_ bh (MachInt ad)      = do putByte bh 3; put_ bh ad
    put_ bh (MachInt64 ae)    = do putByte bh 4; put_ bh ae
    put_ bh (MachWord af)     = do putByte bh 5; put_ bh af
    put_ bh (MachWord64 ag)   = do putByte bh 6; put_ bh ag
    put_ bh (MachFloat ah)    = do putByte bh 7; put_ bh ah
    put_ bh (MachDouble ai)   = do putByte bh 8; put_ bh ai
    put_ bh (MachLabel aj mb fod)
        = do putByte bh 9
             put_ bh aj
             put_ bh mb
             put_ bh fod
    get bh = do
	    h <- getByte bh
	    case h of
	      0 -> do
		    aa <- get bh
		    return (MachChar aa)
	      1 -> do
		    ab <- get bh
		    return (MachStr ab)
	      2 -> do
		    return (MachNullAddr)
	      3 -> do
		    ad <- get bh
		    return (MachInt ad)
	      4 -> do
		    ae <- get bh
		    return (MachInt64 ae)
	      5 -> do
		    af <- get bh
		    return (MachWord af)
	      6 -> do
		    ag <- get bh
		    return (MachWord64 ag)
	      7 -> do
		    ah <- get bh
		    return (MachFloat ah)
	      8 -> do
		    ai <- get bh
		    return (MachDouble ai)
	      9 -> do
		    aj <- get bh
		    mb <- get bh
		    fod <- get bh
		    return (MachLabel aj mb fod)
\end{code}

\begin{code}
instance Outputable Literal where
    ppr lit = pprLit lit

instance Show Literal where
    showsPrec p lit = showsPrecSDoc p (ppr lit)

instance Eq Literal where
    a == b = case (a `compare` b) of { EQ -> True;   _ -> False }
    a /= b = case (a `compare` b) of { EQ -> False;  _ -> True  }

instance Ord Literal where
    a <= b = case (a `compare` b) of { LT -> True;  EQ -> True;  GT -> False }
    a <	 b = case (a `compare` b) of { LT -> True;  EQ -> False; GT -> False }
    a >= b = case (a `compare` b) of { LT -> False; EQ -> True;  GT -> True  }
    a >	 b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True  }
    compare a b = cmpLit a b
\end{code}


	Construction
	~~~~~~~~~~~~
\begin{code}
-- | Creates a 'Literal' of type @Int#@
mkMachInt :: Integer -> Literal
mkMachInt  x   = -- ASSERT2( inIntRange x,  integer x ) 
	 	 -- Not true: you can write out of range Int# literals
		 -- For example, one can write (intToWord# 0xffff0000) to
		 -- get a particular Word bit-pattern, and there's no other
		 -- convenient way to write such literals, which is why we allow it.
		 MachInt x

-- | Creates a 'Literal' of type @Word#@
mkMachWord :: Integer -> Literal
mkMachWord x   = -- ASSERT2( inWordRange x, integer x ) 
		 MachWord x

-- | Creates a 'Literal' of type @Int64#@
mkMachInt64 :: Integer -> Literal
mkMachInt64  x = MachInt64 x

-- | Creates a 'Literal' of type @Word64#@
mkMachWord64 :: Integer -> Literal
mkMachWord64 x = MachWord64 x

-- | Creates a 'Literal' of type @Float#@
mkMachFloat :: Rational -> Literal
mkMachFloat = MachFloat

-- | Creates a 'Literal' of type @Double#@
mkMachDouble :: Rational -> Literal
mkMachDouble = MachDouble

-- | Creates a 'Literal' of type @Char#@
mkMachChar :: Char -> Literal
mkMachChar = MachChar

-- | 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@
mkMachString :: String -> Literal
mkMachString s = MachStr (mkFastString s) -- stored UTF-8 encoded

inIntRange, inWordRange :: Integer -> Bool
inIntRange  x = x >= tARGET_MIN_INT && x <= tARGET_MAX_INT
inWordRange x = x >= 0		    && x <= tARGET_MAX_WORD

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 (MachInt    0) = True
isZeroLit (MachInt64  0) = True
isZeroLit (MachWord   0) = True
isZeroLit (MachWord64 0) = True
isZeroLit (MachFloat  0) = True
isZeroLit (MachDouble 0) = True
isZeroLit _              = False
\end{code}

	Coercions
	~~~~~~~~~
\begin{code}
word2IntLit, int2WordLit,
  narrow8IntLit, narrow16IntLit, narrow32IntLit,
  narrow8WordLit, narrow16WordLit, narrow32WordLit,
  char2IntLit, int2CharLit,
  float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit,
  float2DoubleLit, double2FloatLit
  :: Literal -> Literal

word2IntLit (MachWord w) 
  | w > tARGET_MAX_INT = MachInt (w - tARGET_MAX_WORD - 1)
  | otherwise	       = MachInt w

int2WordLit (MachInt i)
  | i < 0     = MachWord (1 + tARGET_MAX_WORD + i)	-- (-1)  --->  tARGET_MAX_WORD
  | otherwise = MachWord i

narrow8IntLit    (MachInt  i) = MachInt  (toInteger (fromInteger i :: Int8))
narrow16IntLit   (MachInt  i) = MachInt  (toInteger (fromInteger i :: Int16))
narrow32IntLit   (MachInt  i) = MachInt  (toInteger (fromInteger i :: Int32))
narrow8WordLit   (MachWord w) = MachWord (toInteger (fromInteger w :: Word8))
narrow16WordLit  (MachWord w) = MachWord (toInteger (fromInteger w :: Word16))
narrow32WordLit  (MachWord w) = MachWord (toInteger (fromInteger w :: Word32))

char2IntLit (MachChar c) = MachInt  (toInteger (ord c))
int2CharLit (MachInt  i) = MachChar (chr (fromInteger i))

float2IntLit (MachFloat f) = MachInt   (truncate    f)
int2FloatLit (MachInt   i) = MachFloat (fromInteger i)

double2IntLit (MachDouble f) = MachInt    (truncate    f)
int2DoubleLit (MachInt   i) = MachDouble (fromInteger i)

float2DoubleLit (MachFloat  f) = MachDouble f
double2FloatLit (MachDouble d) = MachFloat  d

nullAddrLit :: Literal
nullAddrLit = MachNullAddr
\end{code}

	Predicates
	~~~~~~~~~~
\begin{code}
-- | True if there is absolutely no penalty to duplicating the literal.
-- False principally of strings
litIsTrivial :: Literal -> Bool
--	c.f. CoreUtils.exprIsTrivial
litIsTrivial (MachStr _) = False
litIsTrivial _           = True

-- | True if code space does not go bad if we duplicate this literal
-- Currently we treat it just like 'litIsTrivial'
litIsDupable :: Literal -> Bool
--	c.f. CoreUtils.exprIsDupable
litIsDupable (MachStr _) = False
litIsDupable _           = True

litFitsInChar :: Literal -> Bool
litFitsInChar (MachInt i)
    		         = fromInteger i <= ord minBound 
                        && fromInteger i >= ord maxBound 
litFitsInChar _         = False
\end{code}

	Types
	~~~~~
\begin{code}
-- | Find the Haskell 'Type' the literal occupies
literalType :: Literal -> Type
literalType MachNullAddr    = addrPrimTy
literalType (MachChar _)    = charPrimTy
literalType (MachStr  _)    = addrPrimTy
literalType (MachInt  _)    = intPrimTy
literalType (MachWord  _)   = wordPrimTy
literalType (MachInt64  _)  = int64PrimTy
literalType (MachWord64  _) = word64PrimTy
literalType (MachFloat _)   = floatPrimTy
literalType (MachDouble _)  = doublePrimTy
literalType (MachLabel _ _ _) = addrPrimTy

absentLiteralOf :: TyCon -> Maybe Literal
-- Return a literal of the appropriate primtive
-- TyCon, to use as a placeholder when it doesn't matter
absentLiteralOf tc = lookupUFM absent_lits (tyConName tc)

absent_lits :: UniqFM Literal
absent_lits = listToUFM [ (addrPrimTyConKey,    MachNullAddr)
            		, (charPrimTyConKey,    MachChar 'x')
            		, (intPrimTyConKey,     MachInt 0)
            		, (int64PrimTyConKey,   MachInt64 0)
            		, (floatPrimTyConKey,   MachFloat 0)
            		, (doublePrimTyConKey,  MachDouble 0)
            		, (wordPrimTyConKey,    MachWord 0)
            		, (word64PrimTyConKey,  MachWord64 0) ]
\end{code}


	Comparison
	~~~~~~~~~~
\begin{code}
cmpLit :: Literal -> Literal -> Ordering
cmpLit (MachChar      a)   (MachChar	   b)   = a `compare` b
cmpLit (MachStr       a)   (MachStr	   b)   = a `compare` b
cmpLit (MachNullAddr)      (MachNullAddr)       = EQ
cmpLit (MachInt       a)   (MachInt	   b)   = a `compare` b
cmpLit (MachWord      a)   (MachWord	   b)   = a `compare` b
cmpLit (MachInt64     a)   (MachInt64	   b)   = a `compare` b
cmpLit (MachWord64    a)   (MachWord64	   b)   = a `compare` b
cmpLit (MachFloat     a)   (MachFloat	   b)   = a `compare` b
cmpLit (MachDouble    a)   (MachDouble	   b)   = a `compare` b
cmpLit (MachLabel     a _ _) (MachLabel      b _ _) = a `compare` b
cmpLit lit1		   lit2		        | litTag lit1 <# litTag lit2 = LT
					        | otherwise  		     = GT

litTag :: Literal -> FastInt
litTag (MachChar      _)   = _ILIT(1)
litTag (MachStr       _)   = _ILIT(2)
litTag (MachNullAddr)      = _ILIT(3)
litTag (MachInt       _)   = _ILIT(4)
litTag (MachWord      _)   = _ILIT(5)
litTag (MachInt64     _)   = _ILIT(6)
litTag (MachWord64    _)   = _ILIT(7)
litTag (MachFloat     _)   = _ILIT(8)
litTag (MachDouble    _)   = _ILIT(9)
litTag (MachLabel _ _ _)   = _ILIT(10)
\end{code}

	Printing
	~~~~~~~~
* MachX (i.e. unboxed) things are printed unadornded (e.g. 3, 'a', "foo")
  exceptions: MachFloat gets an initial keyword prefix.

\begin{code}
pprLit :: Literal -> SDoc
pprLit (MachChar ch)  	= pprHsChar ch
pprLit (MachStr s)    	= pprHsString s
pprLit (MachInt i)    	= pprIntVal i
pprLit (MachInt64 i)  	= ptext (sLit "__int64") <+> integer i
pprLit (MachWord w)   	= ptext (sLit "__word") <+> integer w
pprLit (MachWord64 w) 	= ptext (sLit "__word64") <+> integer w
pprLit (MachFloat f)  	= ptext (sLit "__float") <+> rational f
pprLit (MachDouble d) 	= rational d
pprLit (MachNullAddr) 	= ptext (sLit "__NULL")
pprLit (MachLabel l mb fod) = ptext (sLit "__label") <+> b <+> ppr fod
    where b = case mb of
              Nothing -> pprHsString l
              Just x  -> doubleQuotes (text (unpackFS l ++ '@':show x))

pprIntVal :: Integer -> SDoc
-- ^ Print negative integers with parens to be sure it's unambiguous
pprIntVal i | i < 0     = parens (integer i)
	    | otherwise = integer i
\end{code}


%************************************************************************
%*									*
\subsection{Hashing}
%*									*
%************************************************************************

Hash values should be zero or a positive integer.  No negatives please.
(They mess up the UniqFM for some reason.)

\begin{code}
hashLiteral :: Literal -> Int
hashLiteral (MachChar c)    	= ord c + 1000	-- Keep it out of range of common ints
hashLiteral (MachStr s)     	= hashFS s
hashLiteral (MachNullAddr)    	= 0
hashLiteral (MachInt i)   	= hashInteger i
hashLiteral (MachInt64 i) 	= hashInteger i
hashLiteral (MachWord i)   	= hashInteger i
hashLiteral (MachWord64 i) 	= hashInteger i
hashLiteral (MachFloat r)   	= hashRational r
hashLiteral (MachDouble r)  	= hashRational r
hashLiteral (MachLabel s _ _)     = hashFS s

hashRational :: Rational -> Int
hashRational r = hashInteger (numerator r)

hashInteger :: Integer -> Int
hashInteger i = 1 + abs (fromInteger (i `rem` 10000))
		-- The 1+ is to avoid zero, which is a Bad Number
		-- since we use * to combine hash values

hashFS :: FastString -> Int
hashFS s = iBox (uniqueOfFS s)
\end{code}