[project @ 2003-07-29 10:14:57 by simonpj]

[ghc-hetmet.git] / ghc / compiler / coreSyn / CoreSyn.lhs

diff --git a/ghc/compiler/coreSyn/CoreSyn.lhs b/ghc/compiler/coreSyn/CoreSyn.lhs
index 42640f9..a074499 100644 (file)
--- a/ghc/compiler/coreSyn/CoreSyn.lhs
+++ b/ghc/compiler/coreSyn/CoreSyn.lhs
@@ -7,7 +7,7 @@
 module CoreSyn (
        Expr(..), Alt, Bind(..), AltCon(..), Arg, Note(..),
        CoreExpr, CoreAlt, CoreBind, CoreArg, CoreBndr,
-       TaggedExpr, TaggedAlt, TaggedBind, TaggedArg,
+       TaggedExpr, TaggedAlt, TaggedBind, TaggedArg, TaggedBndr(..),
 
        mkLets, mkLams, 
        mkApps, mkTyApps, mkValApps, mkVarApps,
@@ -57,6 +57,7 @@ import Literal                ( Literal, mkMachInt )
 import DataCon         ( DataCon, dataConWorkId )
 import BasicTypes      ( Activation )
 import VarSet
+import FastString
 import Outputable
 \end{code}
 
@@ -78,11 +79,27 @@ data Expr b -- "b" for the type of binders,
   | Lam   b (Expr b)
   | Let   (Bind b) (Expr b)
   | Case  (Expr b) b [Alt b]   -- Binder gets bound to value of scrutinee
-                               -- DEFAULT case must be *first*, if it occurs at all
+       -- Invariant: The list of alternatives is ALWAYS EXHAUSTIVE,
+       --            meaning that it covers all cases that can occur
+       --            See the example below
+       --
+       -- Invariant: The DEFAULT case must be *first*, if it occurs at all
   | Note  Note (Expr b)
   | Type  Type                 -- This should only show up at the top
                                -- level of an Arg
 
+-- An "exhausive" case does not necessarily mention all constructors:
+--     data Foo = Red | Green | Blue
+--
+--     ...case x of 
+--             Red   -> True
+--             other -> f (case x of 
+--                             Green -> ...
+--                             Blue  -> ... )
+-- The inner case does not need a Red alternative, because x can't be Red at
+-- that program point.
+
+
 type Arg b = Expr b            -- Can be a Type
 
 type Alt b = (AltCon, [b], Expr b)     -- (DEFAULT, [], rhs) is the default alternative
@@ -108,6 +125,8 @@ data Note
   | InlineMe           -- Instructs simplifer to treat the enclosed expression
                        -- as very small, and inline it at its call sites
 
+  | CoreNote String     -- A generic core annotation, propagated but not used by GHC
+
 -- NOTE: we also treat expressions wrapped in InlineMe as
 -- 'cheap' and 'dupable' (in the sense of exprIsCheap, exprIsDupable)
 -- What this means is that we obediently inline even things that don't
@@ -165,7 +184,7 @@ rulesRules (Rules rules _) = rules
 \end{code}
 
 \begin{code}
-type RuleName = FAST_STRING
+type RuleName = FastString
 type IdCoreRule = (Id,CoreRule)                -- Rules don't have their leading Id inside them
 
 data CoreRule
@@ -342,12 +361,18 @@ type CoreAlt  = Alt  CoreBndr
 Binders are ``tagged'' with a \tr{t}:
 
 \begin{code}
-type Tagged t = (CoreBndr, t)
+data TaggedBndr t = TB CoreBndr t      -- TB for "tagged binder"
+
+type TaggedBind t = Bind (TaggedBndr t)
+type TaggedExpr t = Expr (TaggedBndr t)
+type TaggedArg  t = Arg  (TaggedBndr t)
+type TaggedAlt  t = Alt  (TaggedBndr t)
+
+instance Outputable b => Outputable (TaggedBndr b) where
+  ppr (TB b l) = char '<' <> ppr b <> comma <> ppr l <> char '>'
 
-type TaggedBind t = Bind (Tagged t)
-type TaggedExpr t = Expr (Tagged t)
-type TaggedArg  t = Arg  (Tagged t)
-type TaggedAlt  t = Alt  (Tagged t)
+instance Outputable b => OutputableBndr (TaggedBndr b) where
+  pprBndr _ b = ppr b  -- Simple
 \end{code}
 
 
@@ -542,6 +567,7 @@ seqExprs [] = ()
 seqExprs (e:es) = seqExpr e `seq` seqExprs es
 
 seqNote (Coerce t1 t2) = seqType t1 `seq` seqType t2
+seqNote (CoreNote s)   = s `seq` ()
 seqNote other         = ()
 
 seqBndr b = b `seq` ()