content: {-
  (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
  
  \section[StgSyn]{Shared term graph (STG) syntax for spineless-tagless code generation}
  
  This data type represents programs just before code generation (conversion to
  @Cmm@): basically, what we have is a stylised form of @CoreSyntax@, the style
  being one that happens to be ideally suited to spineless tagless code
  generation.
  -}
  
  {-# LANGUAGE CPP #-}
  
  module Eta.StgSyn.StgSyn (
          GenStgArg(..),
          GenStgLiveVars,
  
          GenStgBinding(..), GenStgExpr(..), GenStgRhs(..),
          GenStgAlt, AltType(..),
  
          UpdateFlag(..), isUpdatable,
  
          StgBinderInfo,
          noBinderInfo, stgSatOcc, stgUnsatOcc, satCallsOnly,
          combineStgBinderInfo,
  
          -- a set of synonyms for the most common (only :-) parameterisation
          StgArg, StgLiveVars,
          StgBinding, StgExpr, StgRhs, StgAlt,
  
          -- StgOp
          StgOp(..),
  
          -- SRTs
          SRT(..),
  
          -- utils
          stgBindHasCafRefs, stgArgHasCafRefs, stgRhsArity,
          isDllConApp,
          stgArgType, stgArgId,
          stripStgTicksTop,
  
          pprStgBinding, pprStgBindings,
          pprStgLVs
      ) where
  
  #include "HsVersions.h"
  
  import Eta.Core.CoreSyn     ( AltCon, Tickish )
  import Eta.Profiling.CostCentre  ( CostCentreStack )
  import Eta.BasicTypes.DataCon
  import Eta.Main.DynFlags
  import Eta.Utils.FastString
  import Eta.Prelude.ForeignCall ( ForeignCall )
  import Eta.BasicTypes.Id
  import Eta.BasicTypes.IdInfo      ( mayHaveCafRefs )
  import Eta.BasicTypes.Literal     ( Literal, literalType )
  import Eta.BasicTypes.Module      ( Module )
  import Eta.Utils.Outputable
  -- import Eta.Main.Packages    ( isDllName )
  -- import Eta.Utils.Platform
  import Eta.Core.PprCore     ( {- instances -} )
  import Eta.Prelude.PrimOp      ( PrimOp, PrimCall )
  -- import Eta.Types.TyCon       ( PrimRep(..) )
  import Eta.Types.TyCon       ( TyCon )
  import Eta.Types.Type        ( Type )
  -- import Eta.Types.Type        ( typePrimRep )
  import Eta.Utils.UniqSet
  import Eta.BasicTypes.Unique      ( Unique )
  import Eta.Utils.Util
  import Eta.BasicTypes.VarSet      ( IdSet, isEmptyVarSet )
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{@GenStgBinding@}
  *                                                                      *
  ************************************************************************
  
  As usual, expressions are interesting; other things are boring. Here
  are the boring things [except note the @GenStgRhs@], parameterised
  with respect to binder and occurrence information (just as in
  @CoreSyn@):
  
  There is one SRT for each group of bindings.
  -}
  
  data GenStgBinding bndr occ
    = StgNonRec bndr (GenStgRhs bndr occ)
    | StgRec    [(bndr, GenStgRhs bndr occ)]
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{@GenStgArg@}
  *                                                                      *
  ************************************************************************
  -}
  
  data GenStgArg occ
    = StgVarArg  occ
    | StgLitArg  Literal
  
  -- | Does this constructor application refer to
  -- anything in a different *Windows* DLL?
  -- If so, we can't allocate it statically
  isDllConApp :: DynFlags -> Module -> DataCon -> [StgArg] -> Bool
  isDllConApp _dflags _this_mod _con _args = False
  
  -- True of machine addresses; these are the things that don't
  -- work across DLLs. The key point here is that VoidRep comes
  -- out False, so that a top level nullary GADT constructor is
  -- False for isDllConApp
  --    data T a where
  --      T1 :: T Int
  -- gives
  --    T1 :: forall a. (a~Int) -> T a
  -- and hence the top-level binding
  --    $WT1 :: T Int
  --    $WT1 = T1 Int (Coercion (Refl Int))
  -- The coercion argument here gets VoidRep
  -- isAddrRep :: PrimRep -> Bool
  -- isAddrRep AddrRep = True
  -- isAddrRep PtrRep  = True
  -- isAddrRep _       = False
  
  -- | Type of an @StgArg@
  --
  -- Very half baked becase we have lost the type arguments.
  stgArgType :: StgArg -> Type
  stgArgType (StgVarArg v)   = idType v
  stgArgType (StgLitArg lit) = literalType lit
  
  stgArgId :: StgArg -> Maybe Id
  stgArgId (StgVarArg v) = Just v
  stgArgId _             = Nothing
  
  
  -- | Strip ticks of a given type from an STG expression
  stripStgTicksTop :: (Tickish Id -> Bool) -> StgExpr -> ([Tickish Id], StgExpr)
  stripStgTicksTop p = go []
     where go ts (StgTick t e) | p t = go (t:ts) e
           go ts other               = (reverse ts, other)
  
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{STG expressions}
  *                                                                      *
  ************************************************************************
  
  The @GenStgExpr@ data type is parameterised on binder and occurrence
  info, as before.
  
  ************************************************************************
  *                                                                      *
  \subsubsection{@GenStgExpr@ application}
  *                                                                      *
  ************************************************************************
  
  An application is of a function to a list of atoms [not expressions].
  Operationally, we want to push the arguments on the stack and call the
  function. (If the arguments were expressions, we would have to build
  their closures first.)
  
  There is no constructor for a lone variable; it would appear as
  @StgApp var [] _@.
  -}
  
  type GenStgLiveVars occ = UniqSet occ
  
  data GenStgExpr bndr occ
    = StgApp
          occ             -- function
          [GenStgArg occ] -- arguments; may be empty
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{@StgConApp@ and @StgPrimApp@---saturated applications}
  *                                                                      *
  ************************************************************************
  
  There are a specialised forms of application, for constructors,
  primitives, and literals.
  -}
  
    | StgLit      Literal
  
          -- StgConApp is vital for returning unboxed tuples
          -- which can't be let-bound first
    | StgConApp   DataCon
                  [GenStgArg occ] -- Saturated
  
    | StgOpApp    StgOp           -- Primitive op or foreign call
                  [GenStgArg occ] -- Saturated
                  Type            -- Result type
                                  -- We need to know this so that we can
                                  -- assign result registers
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{@StgLam@}
  *                                                                      *
  ************************************************************************
  
  StgLam is used *only* during CoreToStg's work. Before CoreToStg has
  finished it encodes (\x -> e) as (let f = \x -> e in f)
  -}
  
    | StgLam
          [bndr]
          StgExpr    -- Body of lambda
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{@GenStgExpr@: case-expressions}
  *                                                                      *
  ************************************************************************
  
  This has the same boxed/unboxed business as Core case expressions.
  -}
  
    | StgCase
          (GenStgExpr bndr occ)
                      -- the thing to examine
  
          (GenStgLiveVars occ)
                      -- Live vars of whole case expression,
                      -- plus everything that happens after the case
                      -- i.e., those which mustn't be overwritten
  
          (GenStgLiveVars occ)
                      -- Live vars of RHSs (plus what happens afterwards)
                      -- i.e., those which must be saved before eval.
                      --
                      -- note that an alt's constructor's
                      -- binder-variables are NOT counted in the
                      -- free vars for the alt's RHS
  
          bndr        -- binds the result of evaluating the scrutinee
  
          SRT         -- The SRT for the continuation
  
          AltType
  
          [GenStgAlt bndr occ]
                      -- The DEFAULT case is always *first*
                      -- if it is there at all
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{@GenStgExpr@: @let(rec)@-expressions}
  *                                                                      *
  ************************************************************************
  
  The various forms of let(rec)-expression encode most of the
  interesting things we want to do.
  \begin{enumerate}
  \item
  \begin{verbatim}
  let-closure x = [free-vars] [args] expr
  in e
  \end{verbatim}
  is equivalent to
  \begin{verbatim}
  let x = (\free-vars -> \args -> expr) free-vars
  \end{verbatim}
  \tr{args} may be empty (and is for most closures).  It isn't under
  circumstances like this:
  \begin{verbatim}
  let x = (\y -> y+z)
  \end{verbatim}
  This gets mangled to
  \begin{verbatim}
  let-closure x = [z] [y] (y+z)
  \end{verbatim}
  The idea is that we compile code for @(y+z)@ in an environment in which
  @z@ is bound to an offset from \tr{Node}, and @y@ is bound to an
  offset from the stack pointer.
  
  (A let-closure is an @StgLet@ with a @StgRhsClosure@ RHS.)
  
  \item
  \begin{verbatim}
  let-constructor x = Constructor [args]
  in e
  \end{verbatim}
  
  (A let-constructor is an @StgLet@ with a @StgRhsCon@ RHS.)
  
  \item
  Letrec-expressions are essentially the same deal as
  let-closure/let-constructor, so we use a common structure and
  distinguish between them with an @is_recursive@ boolean flag.
  
  \item
  \begin{verbatim}
  let-unboxed u = an arbitrary arithmetic expression in unboxed values
  in e
  \end{verbatim}
  All the stuff on the RHS must be fully evaluated.
  No function calls either!
  
  (We've backed away from this toward case-expressions with
  suitably-magical alts ...)
  
  \item
  ~[Advanced stuff here! Not to start with, but makes pattern matching
  generate more efficient code.]
  
  \begin{verbatim}
  let-escapes-not fail = expr
  in e'
  \end{verbatim}
  Here the idea is that @e'@ guarantees not to put @fail@ in a data structure,
  or pass it to another function. All @e'@ will ever do is tail-call @fail@.
  Rather than build a closure for @fail@, all we need do is to record the stack
  level at the moment of the @let-escapes-not@; then entering @fail@ is just
  a matter of adjusting the stack pointer back down to that point and entering
  the code for it.
  
  Another example:
  \begin{verbatim}
  f x y = let z = huge-expression in
          if y==1 then z else
          if y==2 then z else
          1
  \end{verbatim}
  
  (A let-escapes-not is an @StgLetNoEscape@.)
  
  \item
  We may eventually want:
  \begin{verbatim}
  let-literal x = Literal
  in e
  \end{verbatim}
  \end{enumerate}
  
  And so the code for let(rec)-things:
  -}
  
    | StgLet
          (GenStgBinding bndr occ)    -- right hand sides (see below)
          (GenStgExpr bndr occ)       -- body
  
    | StgLetNoEscape                  -- remember: ``advanced stuff''
          (GenStgLiveVars occ)        -- Live in the whole let-expression
                                      -- Mustn't overwrite these stack slots
                                      -- _Doesn't_ include binders of the let(rec).
  
          (GenStgLiveVars occ)        -- Live in the right hand sides (only)
                                      -- These are the ones which must be saved on
                                      -- the stack if they aren't there already
                                      -- _Does_ include binders of the let(rec) if recursive.
  
          (GenStgBinding bndr occ)    -- right hand sides (see below)
          (GenStgExpr bndr occ)       -- body
  
  {-
  %************************************************************************
  %*                                                                      *
  \subsubsection{@GenStgExpr@: @hpc@, @scc@ and other debug annotations}
  %*                                                                      *
  %************************************************************************
  
  Finally for @hpc@ expressions we introduce a new STG construct.
  -}
  
    | StgTick
      (Tickish bndr)
      (GenStgExpr bndr occ)       -- sub expression
  
  -- END of GenStgExpr
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{STG right-hand sides}
  *                                                                      *
  ************************************************************************
  
  Here's the rest of the interesting stuff for @StgLet@s; the first
  flavour is for closures:
  -}
  
  data GenStgRhs bndr occ
    = StgRhsClosure
          CostCentreStack         -- CCS to be attached (default is CurrentCCS)
          StgBinderInfo           -- Info about how this binder is used (see below)
          [occ]                   -- non-global free vars; a list, rather than
                                  -- a set, because order is important
          !UpdateFlag             -- ReEntrant | Updatable | SingleEntry
          SRT                     -- The SRT reference
          [bndr]                  -- arguments; if empty, then not a function;
                                  -- as above, order is important.
          (GenStgExpr bndr occ)   -- body
  
  {-
  An example may be in order.  Consider:
  \begin{verbatim}
  let t = \x -> \y -> ... x ... y ... p ... q in e
  \end{verbatim}
  Pulling out the free vars and stylising somewhat, we get the equivalent:
  \begin{verbatim}
  let t = (\[p,q] -> \[x,y] -> ... x ... y ... p ...q) p q
  \end{verbatim}
  Stg-operationally, the @[x,y]@ are on the stack, the @[p,q]@ are
  offsets from @Node@ into the closure, and the code ptr for the closure
  will be exactly that in parentheses above.
  
  The second flavour of right-hand-side is for constructors (simple but important):
  -}
  
    | StgRhsCon
          CostCentreStack  -- CCS to be attached (default is CurrentCCS).
                           -- Top-level (static) ones will end up with
                           -- DontCareCCS, because we don't count static
                           -- data in heap profiles, and we don't set CCCS
                           -- from static closure.
          DataCon          -- constructor
          [GenStgArg occ]  -- args
  
  stgRhsArity :: StgRhs -> Int
  stgRhsArity (StgRhsClosure _ _ _ _ _ bndrs _)
    = ASSERT( all isId bndrs ) length bndrs
    -- The arity never includes type parameters, but they should have gone by now
  stgRhsArity (StgRhsCon _ _ _) = 0
  
  stgBindHasCafRefs :: GenStgBinding bndr Id -> Bool
  stgBindHasCafRefs (StgNonRec _ rhs) = rhsHasCafRefs rhs
  stgBindHasCafRefs (StgRec binds)    = any rhsHasCafRefs (map snd binds)
  
  rhsHasCafRefs :: GenStgRhs bndr Id -> Bool
  rhsHasCafRefs (StgRhsClosure _ _ _ upd srt _ _)
    = isUpdatable upd || nonEmptySRT srt
  rhsHasCafRefs (StgRhsCon _ _ args)
    = any stgArgHasCafRefs args
  
  stgArgHasCafRefs :: GenStgArg Id -> Bool
  stgArgHasCafRefs (StgVarArg id) = mayHaveCafRefs (idCafInfo id)
  stgArgHasCafRefs _ = False
  
  -- Here's the @StgBinderInfo@ type, and its combining op:
  
  data StgBinderInfo
    = NoStgBinderInfo
    | SatCallsOnly        -- All occurrences are *saturated* *function* calls
                          -- This means we don't need to build an info table and
                          -- slow entry code for the thing
                          -- Thunks never get this value
  
  noBinderInfo, stgUnsatOcc, stgSatOcc :: StgBinderInfo
  noBinderInfo = NoStgBinderInfo
  stgUnsatOcc  = NoStgBinderInfo
  stgSatOcc    = SatCallsOnly
  
  satCallsOnly :: StgBinderInfo -> Bool
  satCallsOnly SatCallsOnly    = True
  satCallsOnly NoStgBinderInfo = False
  
  combineStgBinderInfo :: StgBinderInfo -> StgBinderInfo -> StgBinderInfo
  combineStgBinderInfo SatCallsOnly SatCallsOnly = SatCallsOnly
  combineStgBinderInfo _            _            = NoStgBinderInfo
  
  --------------
  pp_binder_info :: StgBinderInfo -> SDoc
  pp_binder_info NoStgBinderInfo = empty
  pp_binder_info SatCallsOnly    = ptext (sLit "sat-only")
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection[Stg-case-alternatives]{STG case alternatives}
  *                                                                      *
  ************************************************************************
  
  Very like in @CoreSyntax@ (except no type-world stuff).
  
  The type constructor is guaranteed not to be abstract; that is, we can
  see its representation. This is important because the code generator
  uses it to determine return conventions etc. But it's not trivial
  where there's a moduule loop involved, because some versions of a type
  constructor might not have all the constructors visible. So
  mkStgAlgAlts (in CoreToStg) ensures that it gets the TyCon from the
  constructors or literals (which are guaranteed to have the Real McCoy)
  rather than from the scrutinee type.
  -}
  
  type GenStgAlt bndr occ
    = (AltCon,            -- alts: data constructor,
       [bndr],            -- constructor's parameters,
       [Bool],            -- "use mask", same length as
                          -- parameters; a True in a
                          -- param's position if it is
                          -- used in the ...
       GenStgExpr bndr occ)       -- ...right-hand side.
  
  data AltType
    = PolyAlt             -- Polymorphic (a type variable)
    | UbxTupAlt Int       -- Unboxed tuple of this arity
    | AlgAlt    TyCon     -- Algebraic data type; the AltCons will be DataAlts
    | PrimAlt   TyCon     -- Primitive data type; the AltCons will be LitAlts
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection[Stg]{The Plain STG parameterisation}
  *                                                                      *
  ************************************************************************
  
  This happens to be the only one we use at the moment.
  -}
  
  type StgBinding  = GenStgBinding  Id Id
  type StgArg      = GenStgArg      Id
  type StgLiveVars = GenStgLiveVars Id
  type StgExpr     = GenStgExpr     Id Id
  type StgRhs      = GenStgRhs      Id Id
  type StgAlt      = GenStgAlt      Id Id
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection[UpdateFlag-datatype]{@UpdateFlag@}
  *                                                                      *
  ************************************************************************
  
  This is also used in @LambdaFormInfo@ in the @ClosureInfo@ module.
  
  A @ReEntrant@ closure may be entered multiple times, but should not be
  updated or blackholed. An @Updatable@ closure should be updated after
  evaluation (and may be blackholed during evaluation). A @SingleEntry@
  closure will only be entered once, and so need not be updated but may
  safely be blackholed.
  -}
  
  data UpdateFlag = ReEntrant | Updatable | SingleEntry
  
  instance Outputable UpdateFlag where
      ppr u = char $ case u of
                         ReEntrant   -> 'r'
                         Updatable   -> 'u'
                         SingleEntry -> 's'
  
  isUpdatable :: UpdateFlag -> Bool
  isUpdatable ReEntrant   = False
  isUpdatable SingleEntry = False
  isUpdatable Updatable   = True
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{StgOp}
  *                                                                      *
  ************************************************************************
  
  An StgOp allows us to group together PrimOps and ForeignCalls.
  It's quite useful to move these around together, notably
  in StgOpApp and COpStmt.
  -}
  
  data StgOp
    = StgPrimOp  PrimOp
  
    | StgPrimCallOp PrimCall
  
    | StgFCallOp ForeignCall Unique
          -- The Unique is occasionally needed by the C pretty-printer
          -- (which lacks a unique supply), notably when generating a
          -- typedef for foreign-export-dynamic
  
  instance Outputable StgOp where
      ppr op = case op of
        StgPrimOp op -> ppr op
        StgPrimCallOp primCall -> ppr primCall
        StgFCallOp fc u -> ppr fc <+> brackets (ppr u)
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection[Static Reference Tables]{@SRT@}
  *                                                                      *
  ************************************************************************
  
  There is one SRT per top-level function group. Each local binding and
  case expression within this binding group has a subrange of the whole
  SRT, expressed as an offset and length.
  
  In CoreToStg we collect the list of CafRefs at each SRT site, which is later
  converted into the length and offset form by the SRT pass.
  -}
  
  data SRT
    = NoSRT
    | SRTEntries IdSet
          -- generated by CoreToStg
    | SRT !Int{-offset-} !Int{-length-} -- !Bitmap{-bitmap-}
          -- generated by computeSRTs
  
  nonEmptySRT :: SRT -> Bool
  nonEmptySRT NoSRT           = False
  nonEmptySRT (SRTEntries vs) = not (isEmptyVarSet vs)
  nonEmptySRT _               = True
  
  pprSRT :: SRT -> SDoc
  pprSRT (NoSRT)          = ptext (sLit "_no_srt_")
  pprSRT (SRTEntries ids) = text "SRT:" <> ppr ids
  pprSRT (SRT off _) {-_)-}    = parens (ppr off <> comma <> text "*bitmap*")
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection[Stg-pretty-printing]{Pretty-printing}
  *                                                                      *
  ************************************************************************
  
  Robin Popplestone asked for semi-colon separators on STG binds; here's
  hoping he likes terminators instead...  Ditto for case alternatives.
  -}
  
  pprGenStgBinding :: (OutputableBndr bndr, Outputable bdee, Ord bdee)
                   => GenStgBinding bndr bdee -> SDoc
  
  pprGenStgBinding (StgNonRec bndr rhs)
    = hang (hsep [pprBndr LetBind bndr, equals])
          4 (ppr rhs <> semi)
  
  pprGenStgBinding (StgRec pairs)
    = vcat $ ifPprDebug (ptext $ sLit "{- StgRec (begin) -}") :
             map (ppr_bind) pairs ++ [ifPprDebug $ ptext $ sLit "{- StgRec (end) -}"]
    where
      ppr_bind (bndr, expr)
        = hang (hsep [pprBndr LetBind bndr, equals])
               4 (ppr expr <> semi)
  
  pprStgBinding :: StgBinding -> SDoc
  pprStgBinding  bind  = pprGenStgBinding bind
  
  pprStgBindings :: [StgBinding] -> SDoc
  pprStgBindings binds = vcat (map pprGenStgBinding binds)
  
  instance (Outputable bdee) => Outputable (GenStgArg bdee) where
      ppr = pprStgArg
  
  instance (OutputableBndr bndr, Outputable bdee, Ord bdee)
                  => Outputable (GenStgBinding bndr bdee) where
      ppr = pprGenStgBinding
  
  instance (OutputableBndr bndr, Outputable bdee, Ord bdee)
                  => Outputable (GenStgExpr bndr bdee) where
      ppr = pprStgExpr
  
  instance (OutputableBndr bndr, Outputable bdee, Ord bdee)
                  => Outputable (GenStgRhs bndr bdee) where
      ppr rhs = pprStgRhs rhs
  
  pprStgArg :: (Outputable bdee) => GenStgArg bdee -> SDoc
  pprStgArg (StgVarArg var) = ppr var
  pprStgArg (StgLitArg con) = ppr con
  
  pprStgExpr :: (OutputableBndr bndr, Outputable bdee, Ord bdee)
             => GenStgExpr bndr bdee -> SDoc
  -- special case
  pprStgExpr (StgLit lit)     = ppr lit
  
  -- general case
  pprStgExpr (StgApp func args)
    = hang (ppr func) 4 (sep (map (ppr) args))
  
  pprStgExpr (StgConApp con args)
    = hsep [ ppr con, brackets (interppSP args)]
  
  pprStgExpr (StgOpApp op args _)
    = hsep [ pprStgOp op, brackets (interppSP args)]
  
  pprStgExpr (StgLam bndrs body)
    = sep [ char '\\' <+> ppr_list (map (pprBndr LambdaBind) bndrs)
              <+> ptext (sLit "->"),
           pprStgExpr body ]
    where ppr_list = brackets . fsep . punctuate comma
  
  -- special case: let v = <very specific thing>
  --               in
  --               let ...
  --               in
  --               ...
  --
  -- Very special!  Suspicious! (SLPJ)
  
  {-
  pprStgExpr (StgLet srt (StgNonRec bndr (StgRhsClosure cc bi free_vars upd_flag args rhs))
                          expr@(StgLet _ _))
    = ($$)
        (hang (hcat [ptext (sLit "let { "), ppr bndr, ptext (sLit " = "),
                            ppr cc,
                            pp_binder_info bi,
                            ptext (sLit " ["), ifPprDebug (interppSP free_vars), ptext (sLit "] \\"),
                            ppr upd_flag, ptext (sLit " ["),
                            interppSP args, char ']'])
              8 (sep [hsep [ppr rhs, ptext (sLit "} in")]]))
        (ppr expr)
  -}
  
  -- special case: let ... in let ...
  
  pprStgExpr (StgLet bind expr@(StgLet _ _))
    = ($$)
        (sep [hang (ptext (sLit "let {"))
                  2 (hsep [pprGenStgBinding bind, ptext (sLit "} in")])])
        (ppr expr)
  
  -- general case
  pprStgExpr (StgLet bind expr)
    = sep [hang (ptext (sLit "let {")) 2 (pprGenStgBinding bind),
             hang (ptext (sLit "} in ")) 2 (ppr expr)]
  
  pprStgExpr (StgLetNoEscape lvs_whole lvs_rhss bind expr)
    = sep [hang (ptext (sLit "let-no-escape {"))
                  2 (pprGenStgBinding bind),
             hang (ptext (sLit "} in ") <>
                     ifPprDebug (
                      nest 4 (
                        hcat [ptext  (sLit "-- lvs: ["), interppSP (uniqSetToList lvs_whole),
                               ptext (sLit "]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
                               char ']'])))
                  2 (ppr expr)]
  
  pprStgExpr (StgTick tickish expr)
    = sdocWithDynFlags $ \dflags ->
      if gopt Opt_PprShowTicks dflags
      then sep [ ppr tickish, pprStgExpr expr ]
      else pprStgExpr expr
  
  
  pprStgExpr (StgCase expr lvs_whole lvs_rhss bndr srt alt_type alts)
    = sep [sep [ptext (sLit "case"),
             nest 4 (hsep [pprStgExpr expr,
               ifPprDebug (dcolon <+> ppr alt_type)]),
             ptext (sLit "of"), pprBndr CaseBind bndr, char '{'],
             ifPprDebug (
             nest 4 (
               hcat [ptext  (sLit "-- lvs: ["), interppSP (uniqSetToList lvs_whole),
                      ptext (sLit "]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
                      ptext (sLit "]; "),
                      pprMaybeSRT srt])),
             nest 2 (vcat (map pprStgAlt alts)),
             char '}']
  
  pprStgAlt :: (OutputableBndr bndr, Outputable occ, Ord occ)
            => GenStgAlt bndr occ -> SDoc
  pprStgAlt (con, params, _use_mask, expr)
    = hang (hsep [ppr con, sep (map (pprBndr CaseBind) params), ptext (sLit "->")])
           4 (ppr expr <> semi)
  
  pprStgOp :: StgOp -> SDoc
  pprStgOp (StgPrimOp  op)   = ppr op
  pprStgOp (StgPrimCallOp op)= ppr op
  pprStgOp (StgFCallOp op _) = ppr op
  
  instance Outputable AltType where
    ppr PolyAlt        = ptext (sLit "Polymorphic")
    ppr (UbxTupAlt n)  = ptext (sLit "UbxTup") <+> ppr n
    ppr (AlgAlt tc)    = ptext (sLit "Alg")    <+> ppr tc
    ppr (PrimAlt tc)   = ptext (sLit "Prim")   <+> ppr tc
  
  pprStgLVs :: Outputable occ => GenStgLiveVars occ -> SDoc
  pprStgLVs lvs
    = getPprStyle $ \ sty ->
      if userStyle sty || isEmptyUniqSet lvs then
          empty
      else
          hcat [text "{-lvs:", interpp'SP (uniqSetToList lvs), text "-}"]
  
  pprStgRhs :: (OutputableBndr bndr, Outputable bdee, Ord bdee)
            => GenStgRhs bndr bdee -> SDoc
  
  -- special case
  pprStgRhs (StgRhsClosure cc bi [free_var] upd_flag srt [{-no args-}] (StgApp func []))
    = hcat [ ppr cc,
             pp_binder_info bi,
             brackets (ifPprDebug (ppr free_var)),
             ptext (sLit " \\"), ppr upd_flag, pprMaybeSRT srt, ptext (sLit " [] "), ppr func ]
  
  -- general case
  pprStgRhs (StgRhsClosure cc bi free_vars upd_flag srt args body)
    = sdocWithDynFlags $ \dflags ->
      hang (hsep [if gopt Opt_SccProfilingOn dflags then ppr cc else empty,
                  pp_binder_info bi,
                  ifPprDebug (brackets (interppSP free_vars)),
                  char '\\' <> ppr upd_flag, pprMaybeSRT srt, brackets (interppSP args)])
           4 (ppr body)
  
  pprStgRhs (StgRhsCon cc con args)
    = hcat [ ppr cc,
             space, ppr con, ptext (sLit "! "), brackets (interppSP args)]
  
  pprMaybeSRT :: SRT -> SDoc
  pprMaybeSRT (NoSRT) = empty
  pprMaybeSRT srt     = ptext (sLit "srt:") <> pprSRT srt
  