File: PprC.hs

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{-# LANGUAGE CPP, GADTs #-}

-----------------------------------------------------------------------------
--
-- Pretty-printing of Cmm as C, suitable for feeding gcc
--
-- (c) The University of Glasgow 2004-2006
--
-- Print Cmm as real C, for -fvia-C
--
-- See wiki:Commentary/Compiler/Backends/PprC
--
-- This is simpler than the old PprAbsC, because Cmm is "macro-expanded"
-- relative to the old AbstractC, and many oddities/decorations have
-- disappeared from the data type.
--
-- This code generator is only supported in unregisterised mode.
--
-----------------------------------------------------------------------------

module PprC (
        writeCs,
        pprStringInCStyle
  ) where

#include "HsVersions.h"

-- Cmm stuff
import BlockId
import CLabel
import ForeignCall
import Cmm hiding (pprBBlock)
import PprCmm ()
import Hoopl
import CmmUtils
import CmmSwitch

-- Utils
import CPrim
import DynFlags
import FastString
import Outputable
import Platform
import UniqSet
import Unique
import Util

-- The rest
import Control.Monad.ST
import Data.Bits
import Data.Char
import Data.List
import Data.Map (Map)
import Data.Word
import System.IO
import qualified Data.Map as Map
import Control.Monad (liftM, ap)
#if __GLASGOW_HASKELL__ < 709
import Control.Applicative (Applicative(..))
#endif

import qualified Data.Array.Unsafe as U ( castSTUArray )
import Data.Array.ST

-- --------------------------------------------------------------------------
-- Top level

pprCs :: DynFlags -> [RawCmmGroup] -> SDoc
pprCs dflags cmms
 = pprCode CStyle (vcat $ map (\c -> split_marker $$ pprC c) cmms)
 where
   split_marker
     | gopt Opt_SplitObjs dflags = text "__STG_SPLIT_MARKER"
     | otherwise                 = empty

writeCs :: DynFlags -> Handle -> [RawCmmGroup] -> IO ()
writeCs dflags handle cmms
  = printForC dflags handle (pprCs dflags cmms)

-- --------------------------------------------------------------------------
-- Now do some real work
--
-- for fun, we could call cmmToCmm over the tops...
--

pprC :: RawCmmGroup -> SDoc
pprC tops = vcat $ intersperse blankLine $ map pprTop tops

--
-- top level procs
--
pprTop :: RawCmmDecl -> SDoc
pprTop (CmmProc infos clbl _ graph) =

    (case mapLookup (g_entry graph) infos of
       Nothing -> empty
       Just (Statics info_clbl info_dat) -> pprDataExterns info_dat $$
                                            pprWordArray info_clbl info_dat) $$
    (vcat [
           blankLine,
           extern_decls,
           (if (externallyVisibleCLabel clbl)
                    then mkFN_ else mkIF_) (ppr clbl) <+> lbrace,
           nest 8 temp_decls,
           vcat (map pprBBlock blocks),
           rbrace ]
    )
  where
        blocks = toBlockListEntryFirst graph
        (temp_decls, extern_decls) = pprTempAndExternDecls blocks


-- Chunks of static data.

-- We only handle (a) arrays of word-sized things and (b) strings.

pprTop (CmmData _section (Statics lbl [CmmString str])) =
  hcat [
    pprLocalness lbl, text "char ", ppr lbl,
    text "[] = ", pprStringInCStyle str, semi
  ]

pprTop (CmmData _section (Statics lbl [CmmUninitialised size])) =
  hcat [
    pprLocalness lbl, text "char ", ppr lbl,
    brackets (int size), semi
  ]

pprTop (CmmData _section (Statics lbl lits)) =
  pprDataExterns lits $$
  pprWordArray lbl lits

-- --------------------------------------------------------------------------
-- BasicBlocks are self-contained entities: they always end in a jump.
--
-- Like nativeGen/AsmCodeGen, we could probably reorder blocks to turn
-- as many jumps as possible into fall throughs.
--

pprBBlock :: CmmBlock -> SDoc
pprBBlock block =
  nest 4 (pprBlockId (entryLabel block) <> colon) $$
  nest 8 (vcat (map pprStmt (blockToList nodes)) $$ pprStmt last)
 where
  (_, nodes, last)  = blockSplit block

-- --------------------------------------------------------------------------
-- Info tables. Just arrays of words.
-- See codeGen/ClosureInfo, and nativeGen/PprMach

pprWordArray :: CLabel -> [CmmStatic] -> SDoc
pprWordArray lbl ds
  = sdocWithDynFlags $ \dflags ->
    hcat [ pprLocalness lbl, text "StgWord"
         , space, ppr lbl, text "[]"
         -- See Note [StgWord alignment]
         , pprAlignment (wordWidth dflags)
         , text "= {" ]
    $$ nest 8 (commafy (pprStatics dflags ds))
    $$ text "};"

pprAlignment :: Width -> SDoc
pprAlignment words =
     text "__attribute__((aligned(" <> int (widthInBytes words) <> text ")))"

-- Note [StgWord alignment]
-- C codegen builds static closures as StgWord C arrays (pprWordArray).
-- Their real C type is 'StgClosure'. Macros like UNTAG_CLOSURE assume
-- pointers to 'StgClosure' are aligned at pointer size boundary:
--  4 byte boundary on 32 systems
--  and 8 bytes on 64-bit systems
-- see TAG_MASK and TAG_BITS definition and usage.
--
-- It's a reasonable assumption also known as natural alignment.
-- Although some architectures have different alignment rules.
-- One of known exceptions is m68k (Trac #11395, comment:16) where:
--   __alignof__(StgWord) == 2, sizeof(StgWord) == 4
--
-- Thus we explicitly increase alignment by using
--    __attribute__((aligned(4)))
-- declaration.

--
-- has to be static, if it isn't globally visible
--
pprLocalness :: CLabel -> SDoc
pprLocalness lbl | not $ externallyVisibleCLabel lbl = text "static "
                 | otherwise = empty

-- --------------------------------------------------------------------------
-- Statements.
--

pprStmt :: CmmNode e x -> SDoc

pprStmt stmt =
    sdocWithDynFlags $ \dflags ->
    case stmt of
    CmmEntry{}   -> empty
    CmmComment _ -> empty -- (hang (text "/*") 3 (ftext s)) $$ ptext (sLit "*/")
                          -- XXX if the string contains "*/", we need to fix it
                          -- XXX we probably want to emit these comments when
                          -- some debugging option is on.  They can get quite
                          -- large.

    CmmTick _ -> empty
    CmmUnwind{} -> empty

    CmmAssign dest src -> pprAssign dflags dest src

    CmmStore  dest src
        | typeWidth rep == W64 && wordWidth dflags /= W64
        -> (if isFloatType rep then text "ASSIGN_DBL"
                               else ptext (sLit ("ASSIGN_Word64"))) <>
           parens (mkP_ <> pprExpr1 dest <> comma <> pprExpr src) <> semi

        | otherwise
        -> hsep [ pprExpr (CmmLoad dest rep), equals, pprExpr src <> semi ]
        where
          rep = cmmExprType dflags src

    CmmUnsafeForeignCall target@(ForeignTarget fn conv) results args ->
        fnCall
        where
        (res_hints, arg_hints) = foreignTargetHints target
        hresults = zip results res_hints
        hargs    = zip args arg_hints

        ForeignConvention cconv _ _ ret = conv

        cast_fn = parens (cCast (pprCFunType (char '*') cconv hresults hargs) fn)

        -- See wiki:Commentary/Compiler/Backends/PprC#Prototypes
        fnCall =
            case fn of
              CmmLit (CmmLabel lbl)
                | StdCallConv <- cconv ->
                    pprCall (ppr lbl) cconv hresults hargs
                        -- stdcall functions must be declared with
                        -- a function type, otherwise the C compiler
                        -- doesn't add the @n suffix to the label.  We
                        -- can't add the @n suffix ourselves, because
                        -- it isn't valid C.
                | CmmNeverReturns <- ret ->
                    pprCall cast_fn cconv hresults hargs <> semi
                | not (isMathFun lbl) ->
                    pprForeignCall (ppr lbl) cconv hresults hargs
              _ ->
                    pprCall cast_fn cconv hresults hargs <> semi
                        -- for a dynamic call, no declaration is necessary.

    CmmUnsafeForeignCall (PrimTarget MO_Touch) _results _args -> empty
    CmmUnsafeForeignCall (PrimTarget (MO_Prefetch_Data _)) _results _args -> empty

    CmmUnsafeForeignCall target@(PrimTarget op) results args ->
        fn_call
      where
        cconv = CCallConv
        fn = pprCallishMachOp_for_C op

        (res_hints, arg_hints) = foreignTargetHints target
        hresults = zip results res_hints
        hargs    = zip args arg_hints

        fn_call
          -- The mem primops carry an extra alignment arg.
          -- We could maybe emit an alignment directive using this info.
          -- We also need to cast mem primops to prevent conflicts with GCC
          -- builtins (see bug #5967).
          | Just _align <- machOpMemcpyishAlign op
          = (text ";EFF_(" <> fn <> char ')' <> semi) $$
            pprForeignCall fn cconv hresults hargs
          | otherwise
          = pprCall fn cconv hresults hargs

    CmmBranch ident          -> pprBranch ident
    CmmCondBranch expr yes no _ -> pprCondBranch expr yes no
    CmmCall { cml_target = expr } -> mkJMP_ (pprExpr expr) <> semi
    CmmSwitch arg ids        -> sdocWithDynFlags $ \dflags ->
                                pprSwitch dflags arg ids

    _other -> pprPanic "PprC.pprStmt" (ppr stmt)

type Hinted a = (a, ForeignHint)

pprForeignCall :: SDoc -> CCallConv -> [Hinted CmmFormal] -> [Hinted CmmActual]
               -> SDoc
pprForeignCall fn cconv results args = fn_call
  where
    fn_call = braces (
                 pprCFunType (char '*' <> text "ghcFunPtr") cconv results args <> semi
              $$ text "ghcFunPtr" <+> equals <+> cast_fn <> semi
              $$ pprCall (text "ghcFunPtr") cconv results args <> semi
             )
    cast_fn = parens (parens (pprCFunType (char '*') cconv results args) <> fn)

pprCFunType :: SDoc -> CCallConv -> [Hinted CmmFormal] -> [Hinted CmmActual] -> SDoc
pprCFunType ppr_fn cconv ress args
  = sdocWithDynFlags $ \dflags ->
    let res_type [] = text "void"
        res_type [(one, hint)] = machRepHintCType (localRegType one) hint
        res_type _ = panic "pprCFunType: only void or 1 return value supported"

        arg_type (expr, hint) = machRepHintCType (cmmExprType dflags expr) hint
    in res_type ress <+>
       parens (ccallConvAttribute cconv <> ppr_fn) <>
       parens (commafy (map arg_type args))

-- ---------------------------------------------------------------------
-- unconditional branches
pprBranch :: BlockId -> SDoc
pprBranch ident = text "goto" <+> pprBlockId ident <> semi


-- ---------------------------------------------------------------------
-- conditional branches to local labels
pprCondBranch :: CmmExpr -> BlockId -> BlockId -> SDoc
pprCondBranch expr yes no
        = hsep [ text "if" , parens(pprExpr expr) ,
                        text "goto", pprBlockId yes <> semi,
                        text "else goto", pprBlockId no <> semi ]

-- ---------------------------------------------------------------------
-- a local table branch
--
-- we find the fall-through cases
--
pprSwitch :: DynFlags -> CmmExpr -> SwitchTargets -> SDoc
pprSwitch dflags e ids
  = (hang (text "switch" <+> parens ( pprExpr e ) <+> lbrace)
                4 (vcat ( map caseify pairs ) $$ def)) $$ rbrace
  where
    (pairs, mbdef) = switchTargetsFallThrough ids

    -- fall through case
    caseify (ix:ixs, ident) = vcat (map do_fallthrough ixs) $$ final_branch ix
        where
        do_fallthrough ix =
                 hsep [ text "case" , pprHexVal ix (wordWidth dflags) <> colon ,
                        text "/* fall through */" ]

        final_branch ix =
                hsep [ text "case" , pprHexVal ix (wordWidth dflags) <> colon ,
                       text "goto" , (pprBlockId ident) <> semi ]

    caseify (_     , _    ) = panic "pprSwitch: switch with no cases!"

    def | Just l <- mbdef = text "default: goto" <+> pprBlockId l <> semi
        | otherwise       = empty

-- ---------------------------------------------------------------------
-- Expressions.
--

-- C Types: the invariant is that the C expression generated by
--
--      pprExpr e
--
-- has a type in C which is also given by
--
--      machRepCType (cmmExprType e)
--
-- (similar invariants apply to the rest of the pretty printer).

pprExpr :: CmmExpr -> SDoc
pprExpr e = case e of
    CmmLit lit -> pprLit lit


    CmmLoad e ty -> sdocWithDynFlags $ \dflags -> pprLoad dflags e ty
    CmmReg reg      -> pprCastReg reg
    CmmRegOff reg 0 -> pprCastReg reg

    CmmRegOff reg i
        | i < 0 && negate_ok -> pprRegOff (char '-') (-i)
        | otherwise          -> pprRegOff (char '+') i
      where
        pprRegOff op i' = pprCastReg reg <> op <> int i'
        negate_ok = negate (fromIntegral i :: Integer) <
                    fromIntegral (maxBound::Int)
                     -- overflow is undefined; see #7620

    CmmMachOp mop args -> pprMachOpApp mop args

    CmmStackSlot _ _   -> panic "pprExpr: CmmStackSlot not supported!"


pprLoad :: DynFlags -> CmmExpr -> CmmType -> SDoc
pprLoad dflags e ty
  | width == W64, wordWidth dflags /= W64
  = (if isFloatType ty then text "PK_DBL"
                       else text "PK_Word64")
    <> parens (mkP_ <> pprExpr1 e)

  | otherwise
  = case e of
        CmmReg r | isPtrReg r && width == wordWidth dflags && not (isFloatType ty)
                 -> char '*' <> pprAsPtrReg r

        CmmRegOff r 0 | isPtrReg r && width == wordWidth dflags && not (isFloatType ty)
                      -> char '*' <> pprAsPtrReg r

        CmmRegOff r off | isPtrReg r && width == wordWidth dflags
                        , off `rem` wORD_SIZE dflags == 0 && not (isFloatType ty)
        -- ToDo: check that the offset is a word multiple?
        --       (For tagging to work, I had to avoid unaligned loads. --ARY)
                        -> pprAsPtrReg r <> brackets (ppr (off `shiftR` wordShift dflags))

        _other -> cLoad e ty
  where
    width = typeWidth ty

pprExpr1 :: CmmExpr -> SDoc
pprExpr1 (CmmLit lit)     = pprLit1 lit
pprExpr1 e@(CmmReg _reg)  = pprExpr e
pprExpr1 other            = parens (pprExpr other)

-- --------------------------------------------------------------------------
-- MachOp applications

pprMachOpApp :: MachOp -> [CmmExpr] -> SDoc

pprMachOpApp op args
  | isMulMayOfloOp op
  = text "mulIntMayOflo" <> parens (commafy (map pprExpr args))
  where isMulMayOfloOp (MO_U_MulMayOflo _) = True
        isMulMayOfloOp (MO_S_MulMayOflo _) = True
        isMulMayOfloOp _ = False

pprMachOpApp mop args
  | Just ty <- machOpNeedsCast mop
  = ty <> parens (pprMachOpApp' mop args)
  | otherwise
  = pprMachOpApp' mop args

-- Comparisons in C have type 'int', but we want type W_ (this is what
-- resultRepOfMachOp says).  The other C operations inherit their type
-- from their operands, so no casting is required.
machOpNeedsCast :: MachOp -> Maybe SDoc
machOpNeedsCast mop
  | isComparisonMachOp mop = Just mkW_
  | otherwise              = Nothing

pprMachOpApp' :: MachOp -> [CmmExpr] -> SDoc
pprMachOpApp' mop args
 = case args of
    -- dyadic
    [x,y] -> pprArg x <+> pprMachOp_for_C mop <+> pprArg y

    -- unary
    [x]   -> pprMachOp_for_C mop <> parens (pprArg x)

    _     -> panic "PprC.pprMachOp : machop with wrong number of args"

  where
        -- Cast needed for signed integer ops
    pprArg e | signedOp    mop = sdocWithDynFlags $ \dflags ->
                                 cCast (machRep_S_CType (typeWidth (cmmExprType dflags e))) e
             | needsFCasts mop = sdocWithDynFlags $ \dflags ->
                                 cCast (machRep_F_CType (typeWidth (cmmExprType dflags e))) e
             | otherwise    = pprExpr1 e
    needsFCasts (MO_F_Eq _)   = False
    needsFCasts (MO_F_Ne _)   = False
    needsFCasts (MO_F_Neg _)  = True
    needsFCasts (MO_F_Quot _) = True
    needsFCasts mop  = floatComparison mop

-- --------------------------------------------------------------------------
-- Literals

pprLit :: CmmLit -> SDoc
pprLit lit = case lit of
    CmmInt i rep      -> pprHexVal i rep

    CmmFloat f w       -> parens (machRep_F_CType w) <> str
        where d = fromRational f :: Double
              str | isInfinite d && d < 0 = text "-INFINITY"
                  | isInfinite d          = text "INFINITY"
                  | isNaN d               = text "NAN"
                  | otherwise             = text (show d)
                -- these constants come from <math.h>
                -- see #1861

    CmmVec {} -> panic "PprC printing vector literal"

    CmmBlock bid       -> mkW_ <> pprCLabelAddr (infoTblLbl bid)
    CmmHighStackMark   -> panic "PprC printing high stack mark"
    CmmLabel clbl      -> mkW_ <> pprCLabelAddr clbl
    CmmLabelOff clbl i -> mkW_ <> pprCLabelAddr clbl <> char '+' <> int i
    CmmLabelDiffOff clbl1 _ i
        -- WARNING:
        --  * the lit must occur in the info table clbl2
        --  * clbl1 must be an SRT, a slow entry point or a large bitmap
        -> mkW_ <> pprCLabelAddr clbl1 <> char '+' <> int i

    where
        pprCLabelAddr lbl = char '&' <> ppr lbl

pprLit1 :: CmmLit -> SDoc
pprLit1 lit@(CmmLabelOff _ _) = parens (pprLit lit)
pprLit1 lit@(CmmLabelDiffOff _ _ _) = parens (pprLit lit)
pprLit1 lit@(CmmFloat _ _)    = parens (pprLit lit)
pprLit1 other = pprLit other

-- ---------------------------------------------------------------------------
-- Static data

pprStatics :: DynFlags -> [CmmStatic] -> [SDoc]
pprStatics _ [] = []
pprStatics dflags (CmmStaticLit (CmmFloat f W32) : rest)
  -- floats are padded to a word by padLitToWord, see #1852
  | wORD_SIZE dflags == 8, CmmStaticLit (CmmInt 0 W32) : rest' <- rest
  = pprLit1 (floatToWord dflags f) : pprStatics dflags rest'
  | wORD_SIZE dflags == 4
  = pprLit1 (floatToWord dflags f) : pprStatics dflags rest
  | otherwise
  = pprPanic "pprStatics: float" (vcat (map ppr' rest))
    where ppr' (CmmStaticLit l) = sdocWithDynFlags $ \dflags ->
                                  ppr (cmmLitType dflags l)
          ppr' _other           = text "bad static!"
pprStatics dflags (CmmStaticLit (CmmFloat f W64) : rest)
  = map pprLit1 (doubleToWords dflags f) ++ pprStatics dflags rest

pprStatics dflags (CmmStaticLit (CmmInt i W64) : rest)
  | wordWidth dflags == W32
  = if wORDS_BIGENDIAN dflags
    then pprStatics dflags (CmmStaticLit (CmmInt q W32) :
                            CmmStaticLit (CmmInt r W32) : rest)
    else pprStatics dflags (CmmStaticLit (CmmInt r W32) :
                            CmmStaticLit (CmmInt q W32) : rest)
  where r = i .&. 0xffffffff
        q = i `shiftR` 32
pprStatics dflags (CmmStaticLit (CmmInt _ w) : _)
  | w /= wordWidth dflags
  = panic "pprStatics: cannot emit a non-word-sized static literal"
pprStatics dflags (CmmStaticLit lit : rest)
  = pprLit1 lit : pprStatics dflags rest
pprStatics _ (other : _)
  = pprPanic "pprWord" (pprStatic other)

pprStatic :: CmmStatic -> SDoc
pprStatic s = case s of

    CmmStaticLit lit   -> nest 4 (pprLit lit)
    CmmUninitialised i -> nest 4 (mkC_ <> brackets (int i))

    -- these should be inlined, like the old .hc
    CmmString s'       -> nest 4 (mkW_ <> parens(pprStringInCStyle s'))


-- ---------------------------------------------------------------------------
-- Block Ids

pprBlockId :: BlockId -> SDoc
pprBlockId b = char '_' <> ppr (getUnique b)

-- --------------------------------------------------------------------------
-- Print a MachOp in a way suitable for emitting via C.
--

pprMachOp_for_C :: MachOp -> SDoc

pprMachOp_for_C mop = case mop of

        -- Integer operations
        MO_Add          _ -> char '+'
        MO_Sub          _ -> char '-'
        MO_Eq           _ -> text "=="
        MO_Ne           _ -> text "!="
        MO_Mul          _ -> char '*'

        MO_S_Quot       _ -> char '/'
        MO_S_Rem        _ -> char '%'
        MO_S_Neg        _ -> char '-'

        MO_U_Quot       _ -> char '/'
        MO_U_Rem        _ -> char '%'

        -- & Floating-point operations
        MO_F_Add        _ -> char '+'
        MO_F_Sub        _ -> char '-'
        MO_F_Neg        _ -> char '-'
        MO_F_Mul        _ -> char '*'
        MO_F_Quot       _ -> char '/'

        -- Signed comparisons
        MO_S_Ge         _ -> text ">="
        MO_S_Le         _ -> text "<="
        MO_S_Gt         _ -> char '>'
        MO_S_Lt         _ -> char '<'

        -- & Unsigned comparisons
        MO_U_Ge         _ -> text ">="
        MO_U_Le         _ -> text "<="
        MO_U_Gt         _ -> char '>'
        MO_U_Lt         _ -> char '<'

        -- & Floating-point comparisons
        MO_F_Eq         _ -> text "=="
        MO_F_Ne         _ -> text "!="
        MO_F_Ge         _ -> text ">="
        MO_F_Le         _ -> text "<="
        MO_F_Gt         _ -> char '>'
        MO_F_Lt         _ -> char '<'

        -- Bitwise operations.  Not all of these may be supported at all
        -- sizes, and only integral MachReps are valid.
        MO_And          _ -> char '&'
        MO_Or           _ -> char '|'
        MO_Xor          _ -> char '^'
        MO_Not          _ -> char '~'
        MO_Shl          _ -> text "<<"
        MO_U_Shr        _ -> text ">>" -- unsigned shift right
        MO_S_Shr        _ -> text ">>" -- signed shift right

-- Conversions.  Some of these will be NOPs, but never those that convert
-- between ints and floats.
-- Floating-point conversions use the signed variant.
-- We won't know to generate (void*) casts here, but maybe from
-- context elsewhere

-- noop casts
        MO_UU_Conv from to | from == to -> empty
        MO_UU_Conv _from to -> parens (machRep_U_CType to)

        MO_SS_Conv from to | from == to -> empty
        MO_SS_Conv _from to -> parens (machRep_S_CType to)

        MO_FF_Conv from to | from == to -> empty
        MO_FF_Conv _from to -> parens (machRep_F_CType to)

        MO_SF_Conv _from to -> parens (machRep_F_CType to)
        MO_FS_Conv _from to -> parens (machRep_S_CType to)

        MO_S_MulMayOflo _ -> pprTrace "offending mop:"
                                (text "MO_S_MulMayOflo")
                                (panic $ "PprC.pprMachOp_for_C: MO_S_MulMayOflo"
                                      ++ " should have been handled earlier!")
        MO_U_MulMayOflo _ -> pprTrace "offending mop:"
                                (text "MO_U_MulMayOflo")
                                (panic $ "PprC.pprMachOp_for_C: MO_U_MulMayOflo"
                                      ++ " should have been handled earlier!")

        MO_V_Insert {}    -> pprTrace "offending mop:"
                                (text "MO_V_Insert")
                                (panic $ "PprC.pprMachOp_for_C: MO_V_Insert"
                                      ++ " should have been handled earlier!")
        MO_V_Extract {}   -> pprTrace "offending mop:"
                                (text "MO_V_Extract")
                                (panic $ "PprC.pprMachOp_for_C: MO_V_Extract"
                                      ++ " should have been handled earlier!")

        MO_V_Add {}       -> pprTrace "offending mop:"
                                (text "MO_V_Add")
                                (panic $ "PprC.pprMachOp_for_C: MO_V_Add"
                                      ++ " should have been handled earlier!")
        MO_V_Sub {}       -> pprTrace "offending mop:"
                                (text "MO_V_Sub")
                                (panic $ "PprC.pprMachOp_for_C: MO_V_Sub"
                                      ++ " should have been handled earlier!")
        MO_V_Mul {}       -> pprTrace "offending mop:"
                                (text "MO_V_Mul")
                                (panic $ "PprC.pprMachOp_for_C: MO_V_Mul"
                                      ++ " should have been handled earlier!")

        MO_VS_Quot {}     -> pprTrace "offending mop:"
                                (text "MO_VS_Quot")
                                (panic $ "PprC.pprMachOp_for_C: MO_VS_Quot"
                                      ++ " should have been handled earlier!")
        MO_VS_Rem {}      -> pprTrace "offending mop:"
                                (text "MO_VS_Rem")
                                (panic $ "PprC.pprMachOp_for_C: MO_VS_Rem"
                                      ++ " should have been handled earlier!")
        MO_VS_Neg {}      -> pprTrace "offending mop:"
                                (text "MO_VS_Neg")
                                (panic $ "PprC.pprMachOp_for_C: MO_VS_Neg"
                                      ++ " should have been handled earlier!")

        MO_VU_Quot {}     -> pprTrace "offending mop:"
                                (text "MO_VU_Quot")
                                (panic $ "PprC.pprMachOp_for_C: MO_VU_Quot"
                                      ++ " should have been handled earlier!")
        MO_VU_Rem {}      -> pprTrace "offending mop:"
                                (text "MO_VU_Rem")
                                (panic $ "PprC.pprMachOp_for_C: MO_VU_Rem"
                                      ++ " should have been handled earlier!")

        MO_VF_Insert {}   -> pprTrace "offending mop:"
                                (text "MO_VF_Insert")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Insert"
                                      ++ " should have been handled earlier!")
        MO_VF_Extract {}  -> pprTrace "offending mop:"
                                (text "MO_VF_Extract")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Extract"
                                      ++ " should have been handled earlier!")

        MO_VF_Add {}      -> pprTrace "offending mop:"
                                (text "MO_VF_Add")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Add"
                                      ++ " should have been handled earlier!")
        MO_VF_Sub {}      -> pprTrace "offending mop:"
                                (text "MO_VF_Sub")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Sub"
                                      ++ " should have been handled earlier!")
        MO_VF_Neg {}      -> pprTrace "offending mop:"
                                (text "MO_VF_Neg")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Neg"
                                      ++ " should have been handled earlier!")
        MO_VF_Mul {}      -> pprTrace "offending mop:"
                                (text "MO_VF_Mul")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Mul"
                                      ++ " should have been handled earlier!")
        MO_VF_Quot {}     -> pprTrace "offending mop:"
                                (text "MO_VF_Quot")
                                (panic $ "PprC.pprMachOp_for_C: MO_VF_Quot"
                                      ++ " should have been handled earlier!")

signedOp :: MachOp -> Bool      -- Argument type(s) are signed ints
signedOp (MO_S_Quot _)    = True
signedOp (MO_S_Rem  _)    = True
signedOp (MO_S_Neg  _)    = True
signedOp (MO_S_Ge   _)    = True
signedOp (MO_S_Le   _)    = True
signedOp (MO_S_Gt   _)    = True
signedOp (MO_S_Lt   _)    = True
signedOp (MO_S_Shr  _)    = True
signedOp (MO_SS_Conv _ _) = True
signedOp (MO_SF_Conv _ _) = True
signedOp _                = False

floatComparison :: MachOp -> Bool  -- comparison between float args
floatComparison (MO_F_Eq   _) = True
floatComparison (MO_F_Ne   _) = True
floatComparison (MO_F_Ge   _) = True
floatComparison (MO_F_Le   _) = True
floatComparison (MO_F_Gt   _) = True
floatComparison (MO_F_Lt   _) = True
floatComparison _             = False

-- ---------------------------------------------------------------------
-- tend to be implemented by foreign calls

pprCallishMachOp_for_C :: CallishMachOp -> SDoc

pprCallishMachOp_for_C mop
    = case mop of
        MO_F64_Pwr      -> text "pow"
        MO_F64_Sin      -> text "sin"
        MO_F64_Cos      -> text "cos"
        MO_F64_Tan      -> text "tan"
        MO_F64_Sinh     -> text "sinh"
        MO_F64_Cosh     -> text "cosh"
        MO_F64_Tanh     -> text "tanh"
        MO_F64_Asin     -> text "asin"
        MO_F64_Acos     -> text "acos"
        MO_F64_Atan     -> text "atan"
        MO_F64_Log      -> text "log"
        MO_F64_Exp      -> text "exp"
        MO_F64_Sqrt     -> text "sqrt"
        MO_F32_Pwr      -> text "powf"
        MO_F32_Sin      -> text "sinf"
        MO_F32_Cos      -> text "cosf"
        MO_F32_Tan      -> text "tanf"
        MO_F32_Sinh     -> text "sinhf"
        MO_F32_Cosh     -> text "coshf"
        MO_F32_Tanh     -> text "tanhf"
        MO_F32_Asin     -> text "asinf"
        MO_F32_Acos     -> text "acosf"
        MO_F32_Atan     -> text "atanf"
        MO_F32_Log      -> text "logf"
        MO_F32_Exp      -> text "expf"
        MO_F32_Sqrt     -> text "sqrtf"
        MO_WriteBarrier -> text "write_barrier"
        MO_Memcpy _     -> text "memcpy"
        MO_Memset _     -> text "memset"
        MO_Memmove _    -> text "memmove"
        (MO_BSwap w)    -> ptext (sLit $ bSwapLabel w)
        (MO_PopCnt w)   -> ptext (sLit $ popCntLabel w)
        (MO_Clz w)      -> ptext (sLit $ clzLabel w)
        (MO_Ctz w)      -> ptext (sLit $ ctzLabel w)
        (MO_AtomicRMW w amop) -> ptext (sLit $ atomicRMWLabel w amop)
        (MO_Cmpxchg w)  -> ptext (sLit $ cmpxchgLabel w)
        (MO_AtomicRead w)  -> ptext (sLit $ atomicReadLabel w)
        (MO_AtomicWrite w) -> ptext (sLit $ atomicWriteLabel w)
        (MO_UF_Conv w)  -> ptext (sLit $ word2FloatLabel w)

        MO_S_QuotRem  {} -> unsupported
        MO_U_QuotRem  {} -> unsupported
        MO_U_QuotRem2 {} -> unsupported
        MO_Add2       {} -> unsupported
        MO_SubWordC   {} -> unsupported
        MO_AddIntC    {} -> unsupported
        MO_SubIntC    {} -> unsupported
        MO_U_Mul2     {} -> unsupported
        MO_Touch         -> unsupported
        (MO_Prefetch_Data _ ) -> unsupported
        --- we could support prefetch via "__builtin_prefetch"
        --- Not adding it for now
    where unsupported = panic ("pprCallishMachOp_for_C: " ++ show mop
                            ++ " not supported!")

-- ---------------------------------------------------------------------
-- Useful #defines
--

mkJMP_, mkFN_, mkIF_ :: SDoc -> SDoc

mkJMP_ i = text "JMP_" <> parens i
mkFN_  i = text "FN_"  <> parens i -- externally visible function
mkIF_  i = text "IF_"  <> parens i -- locally visible

-- from includes/Stg.h
--
mkC_,mkW_,mkP_ :: SDoc

mkC_  = text "(C_)"        -- StgChar
mkW_  = text "(W_)"        -- StgWord
mkP_  = text "(P_)"        -- StgWord*

-- ---------------------------------------------------------------------
--
-- Assignments
--
-- Generating assignments is what we're all about, here
--
pprAssign :: DynFlags -> CmmReg -> CmmExpr -> SDoc

-- dest is a reg, rhs is a reg
pprAssign _ r1 (CmmReg r2)
   | isPtrReg r1 && isPtrReg r2
   = hcat [ pprAsPtrReg r1, equals, pprAsPtrReg r2, semi ]

-- dest is a reg, rhs is a CmmRegOff
pprAssign dflags r1 (CmmRegOff r2 off)
   | isPtrReg r1 && isPtrReg r2 && (off `rem` wORD_SIZE dflags == 0)
   = hcat [ pprAsPtrReg r1, equals, pprAsPtrReg r2, op, int off', semi ]
  where
        off1 = off `shiftR` wordShift dflags

        (op,off') | off >= 0  = (char '+', off1)
                  | otherwise = (char '-', -off1)

-- dest is a reg, rhs is anything.
-- We can't cast the lvalue, so we have to cast the rhs if necessary.  Casting
-- the lvalue elicits a warning from new GCC versions (3.4+).
pprAssign _ r1 r2
  | isFixedPtrReg r1             = mkAssign (mkP_ <> pprExpr1 r2)
  | Just ty <- strangeRegType r1 = mkAssign (parens ty <> pprExpr1 r2)
  | otherwise                    = mkAssign (pprExpr r2)
    where mkAssign x = if r1 == CmmGlobal BaseReg
                       then text "ASSIGN_BaseReg" <> parens x <> semi
                       else pprReg r1 <> text " = " <> x <> semi

-- ---------------------------------------------------------------------
-- Registers

pprCastReg :: CmmReg -> SDoc
pprCastReg reg
   | isStrangeTypeReg reg = mkW_ <> pprReg reg
   | otherwise            = pprReg reg

-- True if (pprReg reg) will give an expression with type StgPtr.  We
-- need to take care with pointer arithmetic on registers with type
-- StgPtr.
isFixedPtrReg :: CmmReg -> Bool
isFixedPtrReg (CmmLocal _) = False
isFixedPtrReg (CmmGlobal r) = isFixedPtrGlobalReg r

-- True if (pprAsPtrReg reg) will give an expression with type StgPtr
-- JD: THIS IS HORRIBLE AND SHOULD BE RENAMED, AT THE VERY LEAST.
-- THE GARBAGE WITH THE VNonGcPtr HELPS MATCH THE OLD CODE GENERATOR'S OUTPUT;
-- I'M NOT SURE IF IT SHOULD REALLY STAY THAT WAY.
isPtrReg :: CmmReg -> Bool
isPtrReg (CmmLocal _)                         = False
isPtrReg (CmmGlobal (VanillaReg _ VGcPtr))    = True  -- if we print via pprAsPtrReg
isPtrReg (CmmGlobal (VanillaReg _ VNonGcPtr)) = False -- if we print via pprAsPtrReg
isPtrReg (CmmGlobal reg)                      = isFixedPtrGlobalReg reg

-- True if this global reg has type StgPtr
isFixedPtrGlobalReg :: GlobalReg -> Bool
isFixedPtrGlobalReg Sp    = True
isFixedPtrGlobalReg Hp    = True
isFixedPtrGlobalReg HpLim = True
isFixedPtrGlobalReg SpLim = True
isFixedPtrGlobalReg _     = False

-- True if in C this register doesn't have the type given by
-- (machRepCType (cmmRegType reg)), so it has to be cast.
isStrangeTypeReg :: CmmReg -> Bool
isStrangeTypeReg (CmmLocal _)   = False
isStrangeTypeReg (CmmGlobal g)  = isStrangeTypeGlobal g

isStrangeTypeGlobal :: GlobalReg -> Bool
isStrangeTypeGlobal CCCS                = True
isStrangeTypeGlobal CurrentTSO          = True
isStrangeTypeGlobal CurrentNursery      = True
isStrangeTypeGlobal BaseReg             = True
isStrangeTypeGlobal r                   = isFixedPtrGlobalReg r

strangeRegType :: CmmReg -> Maybe SDoc
strangeRegType (CmmGlobal CCCS) = Just (text "struct CostCentreStack_ *")
strangeRegType (CmmGlobal CurrentTSO) = Just (text "struct StgTSO_ *")
strangeRegType (CmmGlobal CurrentNursery) = Just (text "struct bdescr_ *")
strangeRegType (CmmGlobal BaseReg) = Just (text "struct StgRegTable_ *")
strangeRegType _ = Nothing

-- pprReg just prints the register name.
--
pprReg :: CmmReg -> SDoc
pprReg r = case r of
        CmmLocal  local  -> pprLocalReg local
        CmmGlobal global -> pprGlobalReg global

pprAsPtrReg :: CmmReg -> SDoc
pprAsPtrReg (CmmGlobal (VanillaReg n gcp))
  = WARN( gcp /= VGcPtr, ppr n ) char 'R' <> int n <> text ".p"
pprAsPtrReg other_reg = pprReg other_reg

pprGlobalReg :: GlobalReg -> SDoc
pprGlobalReg gr = case gr of
    VanillaReg n _ -> char 'R' <> int n  <> text ".w"
        -- pprGlobalReg prints a VanillaReg as a .w regardless
        -- Example:     R1.w = R1.w & (-0x8UL);
        --              JMP_(*R1.p);
    FloatReg   n   -> char 'F' <> int n
    DoubleReg  n   -> char 'D' <> int n
    LongReg    n   -> char 'L' <> int n
    Sp             -> text "Sp"
    SpLim          -> text "SpLim"
    Hp             -> text "Hp"
    HpLim          -> text "HpLim"
    CCCS           -> text "CCCS"
    CurrentTSO     -> text "CurrentTSO"
    CurrentNursery -> text "CurrentNursery"
    HpAlloc        -> text "HpAlloc"
    BaseReg        -> text "BaseReg"
    EagerBlackholeInfo -> text "stg_EAGER_BLACKHOLE_info"
    GCEnter1       -> text "stg_gc_enter_1"
    GCFun          -> text "stg_gc_fun"
    other          -> panic $ "pprGlobalReg: Unsupported register: " ++ show other

pprLocalReg :: LocalReg -> SDoc
pprLocalReg (LocalReg uniq _) = char '_' <> ppr uniq

-- -----------------------------------------------------------------------------
-- Foreign Calls

pprCall :: SDoc -> CCallConv -> [Hinted CmmFormal] -> [Hinted CmmActual] -> SDoc
pprCall ppr_fn cconv results args
  | not (is_cishCC cconv)
  = panic $ "pprCall: unknown calling convention"

  | otherwise
  =
    ppr_assign results (ppr_fn <> parens (commafy (map pprArg args))) <> semi
  where
     ppr_assign []           rhs = rhs
     ppr_assign [(one,hint)] rhs
         = pprLocalReg one <> text " = "
                 <> pprUnHint hint (localRegType one) <> rhs
     ppr_assign _other _rhs = panic "pprCall: multiple results"

     pprArg (expr, AddrHint)
        = cCast (text "void *") expr
        -- see comment by machRepHintCType below
     pprArg (expr, SignedHint)
        = sdocWithDynFlags $ \dflags ->
          cCast (machRep_S_CType $ typeWidth $ cmmExprType dflags expr) expr
     pprArg (expr, _other)
        = pprExpr expr

     pprUnHint AddrHint   rep = parens (machRepCType rep)
     pprUnHint SignedHint rep = parens (machRepCType rep)
     pprUnHint _          _   = empty

-- Currently we only have these two calling conventions, but this might
-- change in the future...
is_cishCC :: CCallConv -> Bool
is_cishCC CCallConv    = True
is_cishCC CApiConv     = True
is_cishCC StdCallConv  = True
is_cishCC PrimCallConv = False
is_cishCC JavaScriptCallConv = False

-- ---------------------------------------------------------------------
-- Find and print local and external declarations for a list of
-- Cmm statements.
--
pprTempAndExternDecls :: [CmmBlock] -> (SDoc{-temps-}, SDoc{-externs-})
pprTempAndExternDecls stmts
  = (vcat (map pprTempDecl (uniqSetToList temps)),
     vcat (map (pprExternDecl False{-ToDo-}) (Map.keys lbls)))
  where (temps, lbls) = runTE (mapM_ te_BB stmts)

pprDataExterns :: [CmmStatic] -> SDoc
pprDataExterns statics
  = vcat (map (pprExternDecl False{-ToDo-}) (Map.keys lbls))
  where (_, lbls) = runTE (mapM_ te_Static statics)

pprTempDecl :: LocalReg -> SDoc
pprTempDecl l@(LocalReg _ rep)
  = hcat [ machRepCType rep, space, pprLocalReg l, semi ]

pprExternDecl :: Bool -> CLabel -> SDoc
pprExternDecl _in_srt lbl
  -- do not print anything for "known external" things
  | not (needsCDecl lbl) = empty
  | Just sz <- foreignLabelStdcallInfo lbl = stdcall_decl sz
  | otherwise =
        hcat [ visibility, label_type lbl,
               lparen, ppr lbl, text ");" ]
 where
  label_type lbl | isForeignLabel lbl && isCFunctionLabel lbl = text "FF_"
                 | isCFunctionLabel lbl = text "F_"
                 | otherwise            = text "I_"

  visibility
     | externallyVisibleCLabel lbl = char 'E'
     | otherwise                   = char 'I'

  -- If the label we want to refer to is a stdcall function (on Windows) then
  -- we must generate an appropriate prototype for it, so that the C compiler will
  -- add the @n suffix to the label (#2276)
  stdcall_decl sz = sdocWithDynFlags $ \dflags ->
        text "extern __attribute__((stdcall)) void " <> ppr lbl
        <> parens (commafy (replicate (sz `quot` wORD_SIZE dflags) (machRep_U_CType (wordWidth dflags))))
        <> semi

type TEState = (UniqSet LocalReg, Map CLabel ())
newtype TE a = TE { unTE :: TEState -> (a, TEState) }

instance Functor TE where
      fmap = liftM

instance Applicative TE where
      pure a = TE $ \s -> (a, s)
      (<*>) = ap

instance Monad TE where
   TE m >>= k  = TE $ \s -> case m s of (a, s') -> unTE (k a) s'
   return = pure

te_lbl :: CLabel -> TE ()
te_lbl lbl = TE $ \(temps,lbls) -> ((), (temps, Map.insert lbl () lbls))

te_temp :: LocalReg -> TE ()
te_temp r = TE $ \(temps,lbls) -> ((), (addOneToUniqSet temps r, lbls))

runTE :: TE () -> TEState
runTE (TE m) = snd (m (emptyUniqSet, Map.empty))

te_Static :: CmmStatic -> TE ()
te_Static (CmmStaticLit lit) = te_Lit lit
te_Static _ = return ()

te_BB :: CmmBlock -> TE ()
te_BB block = mapM_ te_Stmt (blockToList mid) >> te_Stmt last
  where (_, mid, last) = blockSplit block

te_Lit :: CmmLit -> TE ()
te_Lit (CmmLabel l) = te_lbl l
te_Lit (CmmLabelOff l _) = te_lbl l
te_Lit (CmmLabelDiffOff l1 _ _) = te_lbl l1
te_Lit _ = return ()

te_Stmt :: CmmNode e x -> TE ()
te_Stmt (CmmAssign r e)         = te_Reg r >> te_Expr e
te_Stmt (CmmStore l r)          = te_Expr l >> te_Expr r
te_Stmt (CmmUnsafeForeignCall target rs es)
  = do  te_Target target
        mapM_ te_temp rs
        mapM_ te_Expr es
te_Stmt (CmmCondBranch e _ _ _) = te_Expr e
te_Stmt (CmmSwitch e _)         = te_Expr e
te_Stmt (CmmCall { cml_target = e }) = te_Expr e
te_Stmt _                       = return ()

te_Target :: ForeignTarget -> TE ()
te_Target (ForeignTarget e _)      = te_Expr e
te_Target (PrimTarget{})           = return ()

te_Expr :: CmmExpr -> TE ()
te_Expr (CmmLit lit)            = te_Lit lit
te_Expr (CmmLoad e _)           = te_Expr e
te_Expr (CmmReg r)              = te_Reg r
te_Expr (CmmMachOp _ es)        = mapM_ te_Expr es
te_Expr (CmmRegOff r _)         = te_Reg r
te_Expr (CmmStackSlot _ _)      = panic "te_Expr: CmmStackSlot not supported!"

te_Reg :: CmmReg -> TE ()
te_Reg (CmmLocal l) = te_temp l
te_Reg _            = return ()


-- ---------------------------------------------------------------------
-- C types for MachReps

cCast :: SDoc -> CmmExpr -> SDoc
cCast ty expr = parens ty <> pprExpr1 expr

cLoad :: CmmExpr -> CmmType -> SDoc
cLoad expr rep
    = sdocWithPlatform $ \platform ->
      if bewareLoadStoreAlignment (platformArch platform)
      then let decl = machRepCType rep <+> text "x" <> semi
               struct = text "struct" <+> braces (decl)
               packed_attr = text "__attribute__((packed))"
               cast = parens (struct <+> packed_attr <> char '*')
           in parens (cast <+> pprExpr1 expr) <> text "->x"
      else char '*' <> parens (cCast (machRepPtrCType rep) expr)
    where -- On these platforms, unaligned loads are known to cause problems
          bewareLoadStoreAlignment ArchAlpha    = True
          bewareLoadStoreAlignment ArchMipseb   = True
          bewareLoadStoreAlignment ArchMipsel   = True
          bewareLoadStoreAlignment (ArchARM {}) = True
          bewareLoadStoreAlignment ArchARM64    = True
          bewareLoadStoreAlignment ArchSPARC    = True
          bewareLoadStoreAlignment ArchSPARC64  = True
          -- Pessimistically assume that they will also cause problems
          -- on unknown arches
          bewareLoadStoreAlignment ArchUnknown  = True
          bewareLoadStoreAlignment _            = False

isCmmWordType :: DynFlags -> CmmType -> Bool
-- True of GcPtrReg/NonGcReg of native word size
isCmmWordType dflags ty = not (isFloatType ty)
                       && typeWidth ty == wordWidth dflags

-- This is for finding the types of foreign call arguments.  For a pointer
-- argument, we always cast the argument to (void *), to avoid warnings from
-- the C compiler.
machRepHintCType :: CmmType -> ForeignHint -> SDoc
machRepHintCType _   AddrHint   = text "void *"
machRepHintCType rep SignedHint = machRep_S_CType (typeWidth rep)
machRepHintCType rep _other     = machRepCType rep

machRepPtrCType :: CmmType -> SDoc
machRepPtrCType r
 = sdocWithDynFlags $ \dflags ->
   if isCmmWordType dflags r then text "P_"
                             else machRepCType r <> char '*'

machRepCType :: CmmType -> SDoc
machRepCType ty | isFloatType ty = machRep_F_CType w
                | otherwise      = machRep_U_CType w
                where
                  w = typeWidth ty

machRep_F_CType :: Width -> SDoc
machRep_F_CType W32 = text "StgFloat" -- ToDo: correct?
machRep_F_CType W64 = text "StgDouble"
machRep_F_CType _   = panic "machRep_F_CType"

machRep_U_CType :: Width -> SDoc
machRep_U_CType w
 = sdocWithDynFlags $ \dflags ->
   case w of
   _ | w == wordWidth dflags -> text "W_"
   W8  -> text "StgWord8"
   W16 -> text "StgWord16"
   W32 -> text "StgWord32"
   W64 -> text "StgWord64"
   _   -> panic "machRep_U_CType"

machRep_S_CType :: Width -> SDoc
machRep_S_CType w
 = sdocWithDynFlags $ \dflags ->
   case w of
   _ | w == wordWidth dflags -> text "I_"
   W8  -> text "StgInt8"
   W16 -> text "StgInt16"
   W32 -> text "StgInt32"
   W64 -> text "StgInt64"
   _   -> panic "machRep_S_CType"


-- ---------------------------------------------------------------------
-- print strings as valid C strings

pprStringInCStyle :: [Word8] -> SDoc
pprStringInCStyle s = doubleQuotes (text (concatMap charToC s))

-- ---------------------------------------------------------------------------
-- Initialising static objects with floating-point numbers.  We can't
-- just emit the floating point number, because C will cast it to an int
-- by rounding it.  We want the actual bit-representation of the float.
--
-- Consider a concrete C example:
--    double d = 2.5e-10;
--    float f  = 2.5e-10f;
--
--    int * i2 = &d;      printf ("i2: %08X %08X\n", i2[0], i2[1]);
--    long long * l = &d; printf (" l: %016llX\n",   l[0]);
--    int * i = &f;       printf (" i: %08X\n",      i[0]);
-- Result on 64-bit LE (x86_64):
--     i2: E826D695 3DF12E0B
--      l: 3DF12E0BE826D695
--      i: 2F89705F
-- Result on 32-bit BE (m68k):
--     i2: 3DF12E0B E826D695
--      l: 3DF12E0BE826D695
--      i: 2F89705F
--
-- The trick here is to notice that binary representation does not
-- change much: only Word32 values get swapped on LE hosts / targets.

-- This is a hack to turn the floating point numbers into ints that we
-- can safely initialise to static locations.

castFloatToWord32Array :: STUArray s Int Float -> ST s (STUArray s Int Word32)
castFloatToWord32Array = U.castSTUArray

castDoubleToWord64Array :: STUArray s Int Double -> ST s (STUArray s Int Word64)
castDoubleToWord64Array = U.castSTUArray

floatToWord :: DynFlags -> Rational -> CmmLit
floatToWord dflags r
  = runST (do
        arr <- newArray_ ((0::Int),0)
        writeArray arr 0 (fromRational r)
        arr' <- castFloatToWord32Array arr
        w32 <- readArray arr' 0
        return (CmmInt (toInteger w32 `shiftL` wo) (wordWidth dflags))
    )
    where wo | wordWidth dflags == W64
             , wORDS_BIGENDIAN dflags    = 32
             | otherwise                 = 0

doubleToWords :: DynFlags -> Rational -> [CmmLit]
doubleToWords dflags r
  = runST (do
        arr <- newArray_ ((0::Int),1)
        writeArray arr 0 (fromRational r)
        arr' <- castDoubleToWord64Array arr
        w64 <- readArray arr' 0
        return (pprWord64 w64)
    )
    where targetWidth = wordWidth dflags
          targetBE    = wORDS_BIGENDIAN dflags
          pprWord64 w64
              | targetWidth == W64 =
                  [ CmmInt (toInteger w64) targetWidth ]
              | targetWidth == W32 =
                  [ CmmInt (toInteger targetW1) targetWidth
                  , CmmInt (toInteger targetW2) targetWidth
                  ]
              | otherwise = panic "doubleToWords.pprWord64"
              where (targetW1, targetW2)
                        | targetBE  = (wHi, wLo)
                        | otherwise = (wLo, wHi)
                    wHi = w64 `shiftR` 32
                    wLo = w64 .&. 0xFFFFffff

-- ---------------------------------------------------------------------------
-- Utils

wordShift :: DynFlags -> Int
wordShift dflags = widthInLog (wordWidth dflags)

commafy :: [SDoc] -> SDoc
commafy xs = hsep $ punctuate comma xs

-- Print in C hex format: 0x13fa
pprHexVal :: Integer -> Width -> SDoc
pprHexVal w rep
  | w < 0     = parens (char '-' <>
                    text "0x" <> intToDoc (-w) <> repsuffix rep)
  | otherwise =     text "0x" <> intToDoc   w  <> repsuffix rep
  where
        -- type suffix for literals:
        -- Integer literals are unsigned in Cmm/C.  We explicitly cast to
        -- signed values for doing signed operations, but at all other
        -- times values are unsigned.  This also helps eliminate occasional
        -- warnings about integer overflow from gcc.

      repsuffix W64 = sdocWithDynFlags $ \dflags ->
               if cINT_SIZE       dflags == 8 then char 'U'
          else if cLONG_SIZE      dflags == 8 then text "UL"
          else if cLONG_LONG_SIZE dflags == 8 then text "ULL"
          else panic "pprHexVal: Can't find a 64-bit type"
      repsuffix _ = char 'U'

      intToDoc :: Integer -> SDoc
      intToDoc i = case truncInt i of
                       0 -> char '0'
                       v -> go v

      -- We need to truncate value as Cmm backend does not drop
      -- redundant bits to ease handling of negative values.
      -- Thus the following Cmm code on 64-bit arch, like amd64:
      --     CInt v;
      --     v = {something};
      --     if (v == %lobits32(-1)) { ...
      -- leads to the following C code:
      --     StgWord64 v = (StgWord32)({something});
      --     if (v == 0xFFFFffffFFFFffffU) { ...
      -- Such code is incorrect as it promotes both operands to StgWord64
      -- and the whole condition is always false.
      truncInt :: Integer -> Integer
      truncInt i =
          case rep of
              W8  -> i `rem` (2^(8 :: Int))
              W16 -> i `rem` (2^(16 :: Int))
              W32 -> i `rem` (2^(32 :: Int))
              W64 -> i `rem` (2^(64 :: Int))
              _   -> panic ("pprHexVal/truncInt: C backend can't encode "
                            ++ show rep ++ " literals")

      go 0 = empty
      go w' = go q <> dig
           where
             (q,r) = w' `quotRem` 16
             dig | r < 10    = char (chr (fromInteger r + ord '0'))
                 | otherwise = char (chr (fromInteger r - 10 + ord 'a'))