Add (a) CoreM monad, (b) new Annotations feature

[ghc-hetmet.git] / compiler / specialise / SpecConstr.lhs

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index 918585c..23127f4 100644 (file)
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -4,6 +4,12 @@
 \section[SpecConstr]{Specialise over constructors}
 
 \begin{code}
 \section[SpecConstr]{Specialise over constructors}
 
 \begin{code}

+-- 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
+

 module SpecConstr(
        specConstrProgram       
     ) where
 module SpecConstr(
        specConstrProgram       
     ) where

@@ -11,33 +17,34 @@ module SpecConstr(
 #include "HsVersions.h"
 
 import CoreSyn
 #include "HsVersions.h"
 
 import CoreSyn

-import CoreLint                ( showPass, endPass )
-import CoreUtils       ( exprType, tcEqExpr, mkPiTypes )
+import CoreSubst
+import CoreUtils
+import CoreUnfold      ( couldBeSmallEnoughToInline )

 import CoreFVs                 ( exprsFreeVars )
 import CoreFVs                 ( exprsFreeVars )

-import CoreSubst       ( Subst, mkSubst, substExpr )
-import CoreTidy                ( tidyRules )
-import PprCore         ( pprRules )

 import WwLib           ( mkWorkerArgs )
 import WwLib           ( mkWorkerArgs )

-import DataCon         ( dataConRepArity, isVanillaDataCon )
-import Type            ( tyConAppArgs, tyVarsOfTypes )
-import Unify           ( coreRefineTys )
-import Id              ( Id, idName, idType, isDataConWorkId_maybe, 
-                         mkUserLocal, mkSysLocal, idUnfolding )
-import Var             ( Var )
+import DataCon         ( dataConRepArity, dataConUnivTyVars )
+import Coercion        
+import Rules
+import Type            hiding( substTy )
+import Id
+import Var

 import VarEnv
 import VarSet
 import VarEnv
 import VarSet

-import Name            ( nameOccName, nameSrcLoc )
-import Rules           ( addIdSpecialisations, mkLocalRule, rulesOfBinds )
+import Name

 import OccName         ( mkSpecOcc )
 import OccName         ( mkSpecOcc )

-import ErrUtils                ( dumpIfSet_dyn )
-import DynFlags                ( DynFlags, DynFlag(..) )
+import DynFlags                ( DynFlags(..) )
+import StaticFlags     ( opt_PprStyle_Debug )
+import StaticFlags     ( opt_SpecInlineJoinPoints )

 import BasicTypes      ( Activation(..) )
 import BasicTypes      ( Activation(..) )

-import Maybes          ( orElse )
-import Util            ( mapAccumL, lengthAtLeast, notNull )
+import Maybes          ( orElse, catMaybes, isJust, isNothing )
+import Util

 import List            ( nubBy, partition )
 import UniqSupply
 import Outputable
 import FastString
 import List            ( nubBy, partition )
 import UniqSupply
 import Outputable
 import FastString

+import UniqFM
+import MonadUtils
+import Control.Monad   ( zipWithM )

 \end{code}
 
 -----------------------------------------------------
 \end{code}
 
 -----------------------------------------------------

@@ -114,7 +121,7 @@ This happens if
 
 Hence the "OR" part of Note [Good arguments] below.
 
 
 Hence the "OR" part of Note [Good arguments] below.
 

-ALTERNATIVE: pass both boxed and unboxed versions.  This no longer saves
+ALTERNATIVE 2: pass both boxed and unboxed versions.  This no longer saves

 allocation, but does perhaps save evals. In the RULE we'd have
 something like
 
 allocation, but does perhaps save evals. In the RULE we'd have
 something like
 

@@ -124,6 +131,25 @@ If at the call site the (I# x) was an unfolding, then we'd have to
 rely on CSE to eliminate the duplicate allocation.... This alternative
 doesn't look attractive enough to pursue.
 
 rely on CSE to eliminate the duplicate allocation.... This alternative
 doesn't look attractive enough to pursue.
 

+ALTERNATIVE 3: ignore the reboxing problem.  The trouble is that 
+the conservative reboxing story prevents many useful functions from being
+specialised.  Example:
+       foo :: Maybe Int -> Int -> Int
+       foo   (Just m) 0 = 0
+       foo x@(Just m) n = foo x (n-m)
+Here the use of 'x' will clearly not require boxing in the specialised function.
+
+The strictness analyser has the same problem, in fact.  Example:
+       f p@(a,b) = ...
+If we pass just 'a' and 'b' to the worker, it might need to rebox the
+pair to create (a,b).  A more sophisticated analysis might figure out
+precisely the cases in which this could happen, but the strictness
+analyser does no such analysis; it just passes 'a' and 'b', and hopes
+for the best.
+
+So my current choice is to make SpecConstr similarly aggressive, and
+ignore the bad potential of reboxing.
+

 
 Note [Good arguments]
 ~~~~~~~~~~~~~~~~~~~~~
 
 Note [Good arguments]
 ~~~~~~~~~~~~~~~~~~~~~

@@ -219,14 +245,8 @@ is to run deShadowBinds before running SpecConstr, but instead we run the
 simplifier.  That gives the simplest possible program for SpecConstr to
 chew on; and it virtually guarantees no shadowing.
 
 simplifier.  That gives the simplest possible program for SpecConstr to
 chew on; and it virtually guarantees no shadowing.
 

------------------------------------------------------
-               Stuff not yet handled
------------------------------------------------------
-
-Here are notes arising from Roman's work that I don't want to lose.
-
-Specialising for constant parameters
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Note [Specialising for constant parameters]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 This one is about specialising on a *constant* (but not necessarily
 constructor) argument
 
 This one is about specialising on a *constant* (but not necessarily
 constructor) argument
 

@@ -268,8 +288,8 @@ When is this worth it?  Call the constant 'lvl'
 
 Also   
 
 
 Also   
 

-Specialising for lambdas
-~~~~~~~~~~~~~~~~~~~~~~~~
+Note [Specialising for lambda parameters]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

     foo :: Int -> (Int -> Int) -> Int
     foo 0 f = 0
     foo m f = foo (f m) (\n -> n-m)
     foo :: Int -> (Int -> Int) -> Int
     foo 0 f = 0
     foo m f = foo (f m) (\n -> n-m)

@@ -304,6 +324,53 @@ may avoid allocating it altogether.  Just like for constructors.
 
 Looks cool, but probably rare...but it might be easy to implement.
 
 
 Looks cool, but probably rare...but it might be easy to implement.
 

+
+Note [SpecConstr for casts]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider 
+    data family T a :: *
+    data instance T Int = T Int
+
+    foo n = ...
+       where
+         go (T 0) = 0
+         go (T n) = go (T (n-1))
+
+The recursive call ends up looking like 
+       go (T (I# ...) `cast` g)
+So we want to spot the construtor application inside the cast.
+That's why we have the Cast case in argToPat
+
+Note [Local recursive groups]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For a *local* recursive group, we can see all the calls to the
+function, so we seed the specialisation loop from the calls in the
+body, not from the calls in the RHS.  Consider:
+
+  bar m n = foo n (n,n) (n,n) (n,n) (n,n)
+   where
+     foo n p q r s
+       | n == 0    = m
+       | n > 3000  = case p of { (p1,p2) -> foo (n-1) (p2,p1) q r s }
+       | n > 2000  = case q of { (q1,q2) -> foo (n-1) p (q2,q1) r s }
+       | n > 1000  = case r of { (r1,r2) -> foo (n-1) p q (r2,r1) s }
+       | otherwise = case s of { (s1,s2) -> foo (n-1) p q r (s2,s1) }
+
+If we start with the RHSs of 'foo', we get lots and lots of specialisations,
+most of which are not needed.  But if we start with the (single) call
+in the rhs of 'bar' we get exactly one fully-specialised copy, and all
+the recursive calls go to this fully-specialised copy. Indeed, the original
+function is later collected as dead code.  This is very important in 
+specialising the loops arising from stream fusion, for example in NDP where
+we were getting literally hundreds of (mostly unused) specialisations of
+a local function.
+
+-----------------------------------------------------
+               Stuff not yet handled
+-----------------------------------------------------
+
+Here are notes arising from Roman's work that I don't want to lose.
+

 Example 1
 ~~~~~~~~~
     data T a = T !a
 Example 1
 ~~~~~~~~~
     data T a = T !a

@@ -382,24 +449,13 @@ unbox the strict fields, becuase T is polymorphic!)
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

-specConstrProgram :: DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind]
-specConstrProgram dflags us binds
-  = do
-       showPass dflags "SpecConstr"
-
-       let (binds', _) = initUs us (go emptyScEnv binds)
-
-       endPass dflags "SpecConstr" Opt_D_dump_spec binds'
-
-       dumpIfSet_dyn dflags Opt_D_dump_rules "Top-level specialisations"
-                 (pprRules (tidyRules emptyTidyEnv (rulesOfBinds binds')))
-
-       return binds'
+specConstrProgram :: DynFlags -> UniqSupply -> [CoreBind] -> [CoreBind]
+specConstrProgram dflags us binds = fst $ initUs us (go (initScEnv dflags) binds)

   where
   where

-    go env []          = returnUs []
-    go env (bind:binds) = scBind env bind      `thenUs` \ (env', _, bind') ->
-                         go env' binds         `thenUs` \ binds' ->
-                         returnUs (bind' : binds')
+    go _   []          = return []
+    go env (bind:binds) = do (env', bind') <- scTopBind env bind
+                             binds' <- go env' binds
+                             return (bind' : binds')

 \end{code}
 
 
 \end{code}
 
 

@@ -410,109 +466,147 @@ specConstrProgram dflags us binds
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

-data ScEnv = SCE { scope :: VarEnv HowBound,
-                       -- Binds all non-top-level variables in scope
+data ScEnv = SCE { sc_size  :: Maybe Int,      -- Size threshold
+                  sc_count :: Maybe Int,       -- Max # of specialisations for any one fn
+
+                  sc_subst :: Subst,           -- Current substitution
+                                               -- Maps InIds to OutExprs

 
 

-                  cons  :: ConstrEnv
+                  sc_how_bound :: HowBoundEnv,
+                       -- Binds interesting non-top-level variables
+                       -- Domain is OutVars (*after* applying the substitution)
+
+                  sc_vals  :: ValueEnv
+                       -- Domain is OutIds (*after* applying the substitution)
+                       -- Used even for top-level bindings (but not imported ones)

             }
 
             }
 

-type ConstrEnv = IdEnv ConValue
-data ConValue  = CV AltCon [CoreArg]
-       -- Variables known to be bound to a constructor
-       -- in a particular case alternative
+---------------------
+-- As we go, we apply a substitution (sc_subst) to the current term
+type InExpr = CoreExpr         -- _Before_ applying the subst

 
 

+type OutExpr = CoreExpr                -- _After_ applying the subst
+type OutId   = Id
+type OutVar  = Var

 
 

-instance Outputable ConValue where
-   ppr (CV con args) = ppr con <+> interpp'SP args
+---------------------
+type HowBoundEnv = VarEnv HowBound     -- Domain is OutVars

 
 

-refineConstrEnv :: Subst -> ConstrEnv -> ConstrEnv
--- The substitution is a type substitution only
-refineConstrEnv subst env = mapVarEnv refine_con_value env
-  where
-    refine_con_value (CV con args) = CV con (map (substExpr subst) args)
+---------------------
+type ValueEnv = IdEnv Value            -- Domain is OutIds
+data Value    = ConVal AltCon [CoreArg]        -- _Saturated_ constructors
+             | LambdaVal               -- Inlinable lambdas or PAPs

 
 

-emptyScEnv = SCE { scope = emptyVarEnv, cons = emptyVarEnv }
+instance Outputable Value where
+   ppr (ConVal con args) = ppr con <+> interpp'SP args
+   ppr LambdaVal        = ptext (sLit "<Lambda>")

 
 

-data HowBound = RecFun         -- These are the recursive functions for which 
-                               -- we seek interesting call patterns
+---------------------
+initScEnv :: DynFlags -> ScEnv
+initScEnv dflags
+  = SCE { sc_size = specConstrThreshold dflags,
+         sc_count = specConstrCount dflags,
+         sc_subst = emptySubst, 
+         sc_how_bound = emptyVarEnv, 
+         sc_vals = emptyVarEnv }

 
 

-             | RecArg          -- These are those functions' arguments; we are
-                               -- interested to see if those arguments are scrutinised
+data HowBound = RecFun -- These are the recursive functions for which 
+                       -- we seek interesting call patterns

 
 

-             | Other           -- We track all others so we know what's in scope
-                               -- This is used in spec_one to check what needs to be
-                               -- passed as a parameter and what is in scope at the 
-                               -- function definition site
+             | RecArg  -- These are those functions' arguments, or their sub-components; 
+                       -- we gather occurrence information for these

 
 instance Outputable HowBound where
   ppr RecFun = text "RecFun"
   ppr RecArg = text "RecArg"
 
 instance Outputable HowBound where
   ppr RecFun = text "RecFun"
   ppr RecArg = text "RecArg"

-  ppr Other = text "Other"
-
-lookupScopeEnv env v = lookupVarEnv (scope env) v
-
-extendBndrs env bndrs = env { scope = extendVarEnvList (scope env) [(b,Other) | b <- bndrs] }
-extendBndr  env bndr  = env { scope = extendVarEnv (scope env) bndr Other }
-
-    -- When we encounter
-    -- case scrut of b
-    --     C x y -> ...
-    -- we want to bind b, and perhaps scrut too, to (C x y)
-extendCaseBndrs :: ScEnv -> Id -> CoreExpr -> AltCon -> [Var] -> ScEnv
-extendCaseBndrs env case_bndr scrut DEFAULT alt_bndrs
-  = extendBndrs env (case_bndr : alt_bndrs)
-
-extendCaseBndrs env case_bndr scrut con@(LitAlt lit) alt_bndrs
-  = ASSERT( null alt_bndrs ) extendAlt env case_bndr scrut (CV con []) []
-
-extendCaseBndrs env case_bndr scrut con@(DataAlt data_con) alt_bndrs
-  | isVanillaDataCon data_con
-  = extendAlt env case_bndr scrut (CV con vanilla_args) alt_bndrs
-    
-  | otherwise  -- GADT
-  = extendAlt env1 case_bndr scrut (CV con gadt_args) alt_bndrs
+
+lookupHowBound :: ScEnv -> Id -> Maybe HowBound
+lookupHowBound env id = lookupVarEnv (sc_how_bound env) id
+
+scSubstId :: ScEnv -> Id -> CoreExpr
+scSubstId env v = lookupIdSubst (sc_subst env) v
+
+scSubstTy :: ScEnv -> Type -> Type
+scSubstTy env ty = substTy (sc_subst env) ty
+
+zapScSubst :: ScEnv -> ScEnv
+zapScSubst env = env { sc_subst = zapSubstEnv (sc_subst env) }
+
+extendScInScope :: ScEnv -> [Var] -> ScEnv
+       -- Bring the quantified variables into scope
+extendScInScope env qvars = env { sc_subst = extendInScopeList (sc_subst env) qvars }
+
+       -- Extend the substitution
+extendScSubst :: ScEnv -> Var -> OutExpr -> ScEnv
+extendScSubst env var expr = env { sc_subst = extendSubst (sc_subst env) var expr }
+
+extendScSubstList :: ScEnv -> [(Var,OutExpr)] -> ScEnv
+extendScSubstList env prs = env { sc_subst = extendSubstList (sc_subst env) prs }
+
+extendHowBound :: ScEnv -> [Var] -> HowBound -> ScEnv
+extendHowBound env bndrs how_bound
+  = env { sc_how_bound = extendVarEnvList (sc_how_bound env)
+                           [(bndr,how_bound) | bndr <- bndrs] }
+
+extendBndrsWith :: HowBound -> ScEnv -> [Var] -> (ScEnv, [Var])
+extendBndrsWith how_bound env bndrs 
+  = (env { sc_subst = subst', sc_how_bound = hb_env' }, bndrs')
+  where
+    (subst', bndrs') = substBndrs (sc_subst env) bndrs
+    hb_env' = sc_how_bound env `extendVarEnvList` 
+                   [(bndr,how_bound) | bndr <- bndrs']
+
+extendBndrWith :: HowBound -> ScEnv -> Var -> (ScEnv, Var)
+extendBndrWith how_bound env bndr 
+  = (env { sc_subst = subst', sc_how_bound = hb_env' }, bndr')

   where
   where

-    vanilla_args = map Type (tyConAppArgs (idType case_bndr)) ++
-                  map varToCoreExpr alt_bndrs
-
-    gadt_args = map (substExpr subst . varToCoreExpr) alt_bndrs
-       -- This call generates some bogus warnings from substExpr,
-       -- because it's inconvenient to put all the Ids in scope
-       -- Will be fixed when we move to FC
-
-    (alt_tvs, _) = span isTyVar alt_bndrs
-    Just (tv_subst, is_local) = coreRefineTys data_con alt_tvs (idType case_bndr)
-    subst = mkSubst in_scope tv_subst emptyVarEnv      -- No Id substitition
-    in_scope = mkInScopeSet (tyVarsOfTypes (varEnvElts tv_subst))
-
-    env1 | is_local  = env
-        | otherwise = env { cons = refineConstrEnv subst (cons env) }
-
-
-
-extendAlt :: ScEnv -> Id -> CoreExpr -> ConValue -> [Var] -> ScEnv
-extendAlt env case_bndr scrut val alt_bndrs
-  = let 
-       env1 = SCE { scope = extendVarEnvList (scope env) [(b,Other) | b <- case_bndr : alt_bndrs],
-                   cons  = extendVarEnv     (cons  env) case_bndr val }
-    in
-    case scrut of
-       Var v ->   -- Bind the scrutinee in the ConstrEnv if it's a variable
-                  -- Also forget if the scrutinee is a RecArg, because we're
-                  -- now in the branch of a case, and we don't want to
-                  -- record a non-scrutinee use of v if we have
-                  --   case v of { (a,b) -> ...(f v)... }
-                SCE { scope = extendVarEnv (scope env1) v Other,
-                      cons  = extendVarEnv (cons env1)  v val }
-       other -> env1
-
-    -- When we encounter a recursive function binding
-    -- f = \x y -> ...
-    -- we want to extend the scope env with bindings 
-    -- that record that f is a RecFn and x,y are RecArgs
-extendRecBndr env fn bndrs
-  =  env { scope = scope env `extendVarEnvList` 
-                  ((fn,RecFun): [(bndr,RecArg) | bndr <- bndrs]) }
+    (subst', bndr') = substBndr (sc_subst env) bndr
+    hb_env' = extendVarEnv (sc_how_bound env) bndr' how_bound
+
+extendRecBndrs :: ScEnv -> [Var] -> (ScEnv, [Var])
+extendRecBndrs env bndrs  = (env { sc_subst = subst' }, bndrs')
+                     where
+                       (subst', bndrs') = substRecBndrs (sc_subst env) bndrs
+
+extendBndr :: ScEnv -> Var -> (ScEnv, Var)
+extendBndr  env bndr  = (env { sc_subst = subst' }, bndr')
+                     where
+                       (subst', bndr') = substBndr (sc_subst env) bndr
+
+extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv
+extendValEnv env _  Nothing   = env
+extendValEnv env id (Just cv) = env { sc_vals = extendVarEnv (sc_vals env) id cv }
+
+extendCaseBndrs :: ScEnv -> Id -> AltCon -> [Var] -> (ScEnv, [Var])
+-- When we encounter
+--     case scrut of b
+--         C x y -> ...
+-- we want to bind b, to (C x y)
+-- NB1: Extends only the sc_vals part of the envt
+-- NB2: Kill the dead-ness info on the pattern binders x,y, since
+--      they are potentially made alive by the [b -> C x y] binding
+extendCaseBndrs env case_bndr con alt_bndrs
+  | isDeadBinder case_bndr
+  = (env, alt_bndrs)
+  | otherwise
+  = (env1, map zap alt_bndrs)
+       -- NB: We used to bind v too, if scrut = (Var v); but
+        --     the simplifer has already done this so it seems
+        --     redundant to do so here
+       -- case scrut of
+       --      Var v  -> extendValEnv env1 v cval
+       --      _other -> env1
+ where
+   zap v | isTyVar v = v               -- See NB2 above
+         | otherwise = zapIdOccInfo v
+   env1 = extendValEnv env case_bndr cval
+   cval = case con of
+               DEFAULT    -> Nothing
+               LitAlt {}  -> Just (ConVal con [])
+               DataAlt {} -> Just (ConVal con vanilla_args)
+                     where
+                       vanilla_args = map Type (tyConAppArgs (idType case_bndr)) ++
+                                      varsToCoreExprs alt_bndrs

 \end{code}
 
 
 \end{code}
 
 

@@ -525,40 +619,110 @@ extendRecBndr env fn bndrs
 \begin{code}
 data ScUsage
    = SCU {
 \begin{code}
 data ScUsage
    = SCU {

-       calls :: !(IdEnv ([Call])),     -- Calls
+       scu_calls :: CallEnv,           -- Calls

                                        -- The functions are a subset of the 
                                        --      RecFuns in the ScEnv
 
                                        -- The functions are a subset of the 
                                        --      RecFuns in the ScEnv
 

-       occs :: !(IdEnv ArgOcc)         -- Information on argument occurrences
-     }                                 -- The variables are a subset of the 
-                                       --      RecArg in the ScEnv
+       scu_occs :: !(IdEnv ArgOcc)     -- Information on argument occurrences
+     }                                 -- The domain is OutIds

 
 

-type Call = (ConstrEnv, [CoreArg])
+type CallEnv = IdEnv [Call]
+type Call = (ValueEnv, [CoreArg])

        -- The arguments of the call, together with the
        -- env giving the constructor bindings at the call site
 
        -- The arguments of the call, together with the
        -- env giving the constructor bindings at the call site
 

-nullUsage = SCU { calls = emptyVarEnv, occs = emptyVarEnv }
+nullUsage :: ScUsage
+nullUsage = SCU { scu_calls = emptyVarEnv, scu_occs = emptyVarEnv }
+
+combineCalls :: CallEnv -> CallEnv -> CallEnv
+combineCalls = plusVarEnv_C (++)

 
 

-combineUsage u1 u2 = SCU { calls = plusVarEnv_C (++) (calls u1) (calls u2),
-                          occs  = plusVarEnv_C combineOcc (occs u1) (occs u2) }
+combineUsage :: ScUsage -> ScUsage -> ScUsage
+combineUsage u1 u2 = SCU { scu_calls = combineCalls (scu_calls u1) (scu_calls u2),
+                          scu_occs  = plusVarEnv_C combineOcc (scu_occs u1) (scu_occs u2) }

 
 

+combineUsages :: [ScUsage] -> ScUsage

 combineUsages [] = nullUsage
 combineUsages us = foldr1 combineUsage us
 
 combineUsages [] = nullUsage
 combineUsages us = foldr1 combineUsage us
 

-data ArgOcc = CaseScrut 
-           | OtherOcc
-           | Both
+lookupOcc :: ScUsage -> OutVar -> (ScUsage, ArgOcc)
+lookupOcc (SCU { scu_calls = sc_calls, scu_occs = sc_occs }) bndr
+  = (SCU {scu_calls = sc_calls, scu_occs = delVarEnv sc_occs bndr},
+     lookupVarEnv sc_occs bndr `orElse` NoOcc)

 
 

-instance Outputable ArgOcc where
-  ppr CaseScrut = ptext SLIT("case-scrut")
-  ppr OtherOcc  = ptext SLIT("other-occ")
-  ppr Both      = ptext SLIT("case-scrut and other")
+lookupOccs :: ScUsage -> [OutVar] -> (ScUsage, [ArgOcc])
+lookupOccs (SCU { scu_calls = sc_calls, scu_occs = sc_occs }) bndrs
+  = (SCU {scu_calls = sc_calls, scu_occs = delVarEnvList sc_occs bndrs},
+     [lookupVarEnv sc_occs b `orElse` NoOcc | b <- bndrs])

 
 

-combineOcc CaseScrut CaseScrut = CaseScrut
-combineOcc OtherOcc  OtherOcc  = OtherOcc
-combineOcc _        _         = Both
-\end{code}
+data ArgOcc = NoOcc    -- Doesn't occur at all; or a type argument
+           | UnkOcc    -- Used in some unknown way
+
+           | ScrutOcc (UniqFM [ArgOcc])        -- See Note [ScrutOcc]
+
+           | BothOcc   -- Definitely taken apart, *and* perhaps used in some other way
+
+{-     Note  [ScrutOcc]

 
 

+An occurrence of ScrutOcc indicates that the thing, or a `cast` version of the thing,
+is *only* taken apart or applied.
+
+  Functions, literal: ScrutOcc emptyUFM
+  Data constructors:  ScrutOcc subs,
+
+where (subs :: UniqFM [ArgOcc]) gives usage of the *pattern-bound* components,
+The domain of the UniqFM is the Unique of the data constructor
+
+The [ArgOcc] is the occurrences of the *pattern-bound* components 
+of the data structure.  E.g.
+       data T a = forall b. MkT a b (b->a)
+A pattern binds b, x::a, y::b, z::b->a, but not 'a'!
+
+-}
+
+instance Outputable ArgOcc where
+  ppr (ScrutOcc xs) = ptext (sLit "scrut-occ") <> ppr xs
+  ppr UnkOcc       = ptext (sLit "unk-occ")
+  ppr BothOcc      = ptext (sLit "both-occ")
+  ppr NoOcc                = ptext (sLit "no-occ")
+
+-- Experimentally, this vesion of combineOcc makes ScrutOcc "win", so
+-- that if the thing is scrutinised anywhere then we get to see that
+-- in the overall result, even if it's also used in a boxed way
+-- This might be too agressive; see Note [Reboxing] Alternative 3
+combineOcc :: ArgOcc -> ArgOcc -> ArgOcc
+combineOcc NoOcc        occ           = occ
+combineOcc occ                  NoOcc         = occ
+combineOcc (ScrutOcc xs) (ScrutOcc ys) = ScrutOcc (plusUFM_C combineOccs xs ys)
+combineOcc _occ          (ScrutOcc ys) = ScrutOcc ys
+combineOcc (ScrutOcc xs) _occ         = ScrutOcc xs
+combineOcc UnkOcc        UnkOcc        = UnkOcc
+combineOcc _       _                  = BothOcc
+
+combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
+combineOccs xs ys = zipWithEqual "combineOccs" combineOcc xs ys
+
+setScrutOcc :: ScEnv -> ScUsage -> OutExpr -> ArgOcc -> ScUsage
+-- _Overwrite_ the occurrence info for the scrutinee, if the scrutinee
+-- is a variable, and an interesting variable
+setScrutOcc env usg (Cast e _) occ = setScrutOcc env usg e occ
+setScrutOcc env usg (Note _ e) occ = setScrutOcc env usg e occ
+setScrutOcc env usg (Var v)    occ
+  | Just RecArg <- lookupHowBound env v = usg { scu_occs = extendVarEnv (scu_occs usg) v occ }
+  | otherwise                          = usg
+setScrutOcc _env usg _other _occ       -- Catch-all
+  = usg        
+
+conArgOccs :: ArgOcc -> AltCon -> [ArgOcc]
+-- Find usage of components of data con; returns [UnkOcc...] if unknown
+-- See Note [ScrutOcc] for the extra UnkOccs in the vanilla datacon case
+
+conArgOccs (ScrutOcc fm) (DataAlt dc) 
+  | Just pat_arg_occs <- lookupUFM fm dc
+  = [UnkOcc | _ <- dataConUnivTyVars dc] ++ pat_arg_occs
+
+conArgOccs _other _con = repeat UnkOcc
+\end{code}

 
 %************************************************************************
 %*                                                                     *
 
 %************************************************************************
 %*                                                                     *

@@ -570,155 +734,323 @@ The main recursive function gathers up usage information, and
 creates specialised versions of functions.
 
 \begin{code}
 creates specialised versions of functions.
 
 \begin{code}

-scExpr :: ScEnv -> CoreExpr -> UniqSM (ScUsage, CoreExpr)
+scExpr, scExpr' :: ScEnv -> CoreExpr -> UniqSM (ScUsage, CoreExpr)

        -- The unique supply is needed when we invent
        -- a new name for the specialised function and its args
 
        -- The unique supply is needed when we invent
        -- a new name for the specialised function and its args
 

-scExpr env e@(Type t) = returnUs (nullUsage, e)
-scExpr env e@(Lit l)  = returnUs (nullUsage, e)
-scExpr env e@(Var v)  = returnUs (varUsage env v OtherOcc, e)
-scExpr env (Note n e) = scExpr env e   `thenUs` \ (usg,e') ->
-                       returnUs (usg, Note n e')
-scExpr env (Lam b e)  = scExpr (extendBndr env b) e    `thenUs` \ (usg,e') ->
-                       returnUs (usg, Lam b e')
-
-scExpr env (Case scrut b ty alts) 
-  = sc_scrut scrut             `thenUs` \ (scrut_usg, scrut') ->
-    mapAndUnzipUs sc_alt alts  `thenUs` \ (alts_usgs, alts') ->
-    returnUs (combineUsages alts_usgs `combineUsage` scrut_usg,
-             Case scrut' b ty alts')
+scExpr env e = scExpr' env e
+
+
+scExpr' env (Var v)     = case scSubstId env v of
+                           Var v' -> return (varUsage env v' UnkOcc, Var v')
+                           e'     -> scExpr (zapScSubst env) e'
+
+scExpr' env (Type t)    = return (nullUsage, Type (scSubstTy env t))
+scExpr' _   e@(Lit {})  = return (nullUsage, e)
+scExpr' env (Note n e)  = do (usg,e') <- scExpr env e
+                             return (usg, Note n e')
+scExpr' env (Cast e co) = do (usg, e') <- scExpr env e
+                             return (usg, Cast e' (scSubstTy env co))
+scExpr' env e@(App _ _) = scApp env (collectArgs e)
+scExpr' env (Lam b e)   = do let (env', b') = extendBndr env b
+                             (usg, e') <- scExpr env' e
+                             return (usg, Lam b' e')
+
+scExpr' env (Case scrut b ty alts) 
+  = do { (scrut_usg, scrut') <- scExpr env scrut
+       ; case isValue (sc_vals env) scrut' of
+               Just (ConVal con args) -> sc_con_app con args scrut'
+               _other                 -> sc_vanilla scrut_usg scrut'
+       }

   where
   where

-    sc_scrut e@(Var v) = returnUs (varUsage env v CaseScrut, e)
-    sc_scrut e        = scExpr env e
-
-    sc_alt (con,bs,rhs) = scExpr env1 rhs      `thenUs` \ (usg,rhs') ->
-                         returnUs (usg, (con,bs,rhs'))
-                       where
-                         env1 = extendCaseBndrs env b scrut con bs
-
-scExpr env (Let bind body)
-  = scBind env bind    `thenUs` \ (env', bind_usg, bind') ->
-    scExpr env' body   `thenUs` \ (body_usg, body') ->
-    returnUs (bind_usg `combineUsage` body_usg, Let bind' body')
-
-scExpr env e@(App _ _) 
-  = let 
-       (fn, args) = collectArgs e
-    in
-    mapAndUnzipUs (scExpr env) (fn:args)       `thenUs` \ (usgs, (fn':args')) ->
-       -- Process the function too.   It's almost always a variable,
-       -- but not always.  In particular, if this pass follows float-in,
-       -- which it may, we can get 
-       --      (let f = ...f... in f) arg1 arg2
-    let
-       call_usg = case fn of
-                       Var f | Just RecFun <- lookupScopeEnv env f
-                             -> SCU { calls = unitVarEnv f [(cons env, args)], 
-                                      occs  = emptyVarEnv }
-                       other -> nullUsage
-    in
-    returnUs (combineUsages usgs `combineUsage` call_usg, mkApps fn' args')
+    sc_con_app con args scrut'         -- Known constructor; simplify
+       = do { let (_, bs, rhs) = findAlt con alts
+                  alt_env' = extendScSubstList env ((b,scrut') : bs `zip` trimConArgs con args)
+            ; scExpr alt_env' rhs }
+                               
+    sc_vanilla scrut_usg scrut'        -- Normal case
+     = do { let (alt_env,b') = extendBndrWith RecArg env b
+                       -- Record RecArg for the components
+
+         ; (alt_usgs, alt_occs, alts')
+               <- mapAndUnzip3M (sc_alt alt_env scrut' b') alts
+
+         ; let (alt_usg, b_occ) = lookupOcc (combineUsages alt_usgs) b'
+               scrut_occ        = foldr combineOcc b_occ alt_occs
+               scrut_usg'       = setScrutOcc env scrut_usg scrut' scrut_occ
+               -- The combined usage of the scrutinee is given
+               -- by scrut_occ, which is passed to scScrut, which
+               -- in turn treats a bare-variable scrutinee specially
+
+         ; return (alt_usg `combineUsage` scrut_usg',
+                   Case scrut' b' (scSubstTy env ty) alts') }
+
+    sc_alt env _scrut' b' (con,bs,rhs)
+      = do { let (env1, bs1)  = extendBndrsWith RecArg env bs
+                (env2, bs2) = extendCaseBndrs env1 b' con bs1
+          ; (usg,rhs') <- scExpr env2 rhs
+          ; let (usg', arg_occs) = lookupOccs usg bs2
+                scrut_occ = case con of
+                               DataAlt dc -> ScrutOcc (unitUFM dc arg_occs)
+                               _          -> ScrutOcc emptyUFM
+          ; return (usg', scrut_occ, (con, bs2, rhs')) }
+
+scExpr' env (Let (NonRec bndr rhs) body)
+  | isTyVar bndr       -- Type-lets may be created by doBeta
+  = scExpr' (extendScSubst env bndr rhs) body
+  | otherwise
+  = do { let (body_env, bndr') = extendBndr env bndr
+       ; (rhs_usg, (_, args', rhs_body', _)) <- scRecRhs env (bndr',rhs)
+       ; let rhs' = mkLams args' rhs_body'
+
+       ; if not opt_SpecInlineJoinPoints || null args' || isEmptyVarEnv (scu_calls rhs_usg) then do
+           do  {       -- Vanilla case
+                 let body_env2 = extendValEnv body_env bndr' (isValue (sc_vals env) rhs')
+                       -- Record if the RHS is a value
+               ; (body_usg, body') <- scExpr body_env2 body
+               ; return (body_usg `combineUsage` rhs_usg, Let (NonRec bndr' rhs') body') }
+         else  -- For now, just brutally inline the join point
+           do { let body_env2 = extendScSubst env bndr rhs'
+              ; scExpr body_env2 body } }
+       

 
 

+{-  Old code
+           do  {       -- Join-point case
+                 let body_env2 = extendHowBound body_env [bndr'] RecFun
+                       -- If the RHS of this 'let' contains calls
+                       -- to recursive functions that we're trying
+                       -- to specialise, then treat this let too
+                       -- as one to specialise
+               ; (body_usg, body') <- scExpr body_env2 body
+
+               ; (spec_usg, _, specs) <- specialise env (scu_calls body_usg) ([], rhs_info)
+
+               ; return (body_usg { scu_calls = scu_calls body_usg `delVarEnv` bndr' } 
+                         `combineUsage` rhs_usg `combineUsage` spec_usg,
+                         mkLets [NonRec b r | (b,r) <- specInfoBinds rhs_info specs] body')
+       }
+-}

 
 

-----------------------
-scBind :: ScEnv -> CoreBind -> UniqSM (ScEnv, ScUsage, CoreBind)
-scBind env (Rec [(fn,rhs)])
-  | notNull val_bndrs
-  = scExpr env_fn_body body            `thenUs` \ (usg, body') ->
-    specialise env fn bndrs body' usg  `thenUs` \ (rules, spec_prs) ->
-       -- Note body': the specialised copies should be based on the 
-       --             optimised version of the body, in case there were
-       --             nested functions inside.
-    let
-       SCU { calls = calls, occs = occs } = usg
-    in
-    returnUs (extendBndr env fn,       -- For the body of the letrec, just
-                                       -- extend the env with Other to record 
-                                       -- that it's in scope; no funny RecFun business
-             SCU { calls = calls `delVarEnv` fn, occs = occs `delVarEnvList` val_bndrs},
-             Rec ((fn `addIdSpecialisations` rules, mkLams bndrs body') : spec_prs))
+-- A *local* recursive group: see Note [Local recursive groups]
+scExpr' env (Let (Rec prs) body)
+  = do { let (bndrs,rhss) = unzip prs
+             (rhs_env1,bndrs') = extendRecBndrs env bndrs
+             rhs_env2 = extendHowBound rhs_env1 bndrs' RecFun
+
+       ; (rhs_usgs, rhs_infos) <- mapAndUnzipM (scRecRhs rhs_env2) (bndrs' `zip` rhss)
+       ; (body_usg, body')     <- scExpr rhs_env2 body
+
+       -- NB: start specLoop from body_usg
+       ; (spec_usg, specs) <- specLoop rhs_env2 (scu_calls body_usg) rhs_infos nullUsage
+                                       [SI [] 0 (Just usg) | usg <- rhs_usgs]
+
+       ; let all_usg = spec_usg `combineUsage` body_usg
+             bind'   = Rec (concat (zipWith specInfoBinds rhs_infos specs))
+
+       ; return (all_usg { scu_calls = scu_calls all_usg `delVarEnvList` bndrs' },
+                 Let bind' body') }
+
+-----------------------------------
+scApp :: ScEnv -> (InExpr, [InExpr]) -> UniqSM (ScUsage, CoreExpr)
+
+scApp env (Var fn, args)       -- Function is a variable
+  = ASSERT( not (null args) )
+    do { args_w_usgs <- mapM (scExpr env) args
+       ; let (arg_usgs, args') = unzip args_w_usgs
+             arg_usg = combineUsages arg_usgs
+       ; case scSubstId env fn of
+           fn'@(Lam {}) -> scExpr (zapScSubst env) (doBeta fn' args')
+                       -- Do beta-reduction and try again
+
+           Var fn' -> return (arg_usg `combineUsage` fn_usg, mkApps (Var fn') args')
+               where
+                 fn_usg = case lookupHowBound env fn' of
+                               Just RecFun -> SCU { scu_calls = unitVarEnv fn' [(sc_vals env, args')], 
+                                                    scu_occs  = emptyVarEnv }
+                               Just RecArg -> SCU { scu_calls = emptyVarEnv,
+                                                    scu_occs  = unitVarEnv fn' (ScrutOcc emptyUFM) }
+                               Nothing     -> nullUsage
+
+
+           other_fn' -> return (arg_usg, mkApps other_fn' args') }
+               -- NB: doing this ignores any usage info from the substituted
+               --     function, but I don't think that matters.  If it does
+               --     we can fix it.

   where
   where

-    (bndrs,body) = collectBinders rhs
-    val_bndrs    = filter isId bndrs
-    env_fn_body         = extendRecBndr env fn bndrs
+    doBeta :: OutExpr -> [OutExpr] -> OutExpr
+    -- ToDo: adjust for System IF
+    doBeta (Lam bndr body) (arg : args) = Let (NonRec bndr arg) (doBeta body args)
+    doBeta fn             args         = mkApps fn args
+
+-- The function is almost always a variable, but not always.  
+-- In particular, if this pass follows float-in,
+-- which it may, we can get 
+--     (let f = ...f... in f) arg1 arg2
+scApp env (other_fn, args)
+  = do         { (fn_usg,   fn')   <- scExpr env other_fn
+       ; (arg_usgs, args') <- mapAndUnzipM (scExpr env) args
+       ; return (combineUsages arg_usgs `combineUsage` fn_usg, mkApps fn' args') }

 
 

-scBind env (Rec prs)
-  = mapAndUnzipUs do_one prs   `thenUs` \ (usgs, prs') ->
-    returnUs (extendBndrs env (map fst prs), combineUsages usgs, Rec prs')
+----------------------
+scTopBind :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
+scTopBind env (Rec prs)
+  | Just threshold <- sc_size env
+  , not (all (couldBeSmallEnoughToInline threshold) rhss)
+               -- No specialisation
+  = do { let (rhs_env,bndrs') = extendRecBndrs env bndrs
+       ; (_, rhss') <- mapAndUnzipM (scExpr rhs_env) rhss
+       ; return (rhs_env, Rec (bndrs' `zip` rhss')) }
+  | otherwise  -- Do specialisation
+  = do { let (rhs_env1,bndrs') = extendRecBndrs env bndrs
+             rhs_env2 = extendHowBound rhs_env1 bndrs' RecFun
+
+       ; (rhs_usgs, rhs_infos) <- mapAndUnzipM (scRecRhs rhs_env2) (bndrs' `zip` rhss)
+       ; let rhs_usg = combineUsages rhs_usgs
+
+       ; (_, specs) <- specLoop rhs_env2 (scu_calls rhs_usg) rhs_infos nullUsage
+                                [SI [] 0 Nothing | _ <- bndrs]
+
+       ; return (rhs_env1,  -- For the body of the letrec, delete the RecFun business
+                 Rec (concat (zipWith specInfoBinds rhs_infos specs))) }

   where
   where

-    do_one (bndr,rhs) = scExpr env rhs `thenUs` \ (usg, rhs') ->
-                       returnUs (usg, (bndr,rhs'))
+    (bndrs,rhss) = unzip prs
+
+scTopBind env (NonRec bndr rhs)
+  = do { (_, rhs') <- scExpr env rhs
+       ; let (env1, bndr') = extendBndr env bndr
+             env2 = extendValEnv env1 bndr' (isValue (sc_vals env) rhs')
+       ; return (env2, NonRec bndr' rhs') }

 
 

-scBind env (NonRec bndr rhs)
-  = scExpr env rhs     `thenUs` \ (usg, rhs') ->
-    returnUs (extendBndr env bndr, usg, NonRec bndr rhs')
+----------------------
+scRecRhs :: ScEnv -> (OutId, InExpr) -> UniqSM (ScUsage, RhsInfo)
+scRecRhs env (bndr,rhs)
+  = do { let (arg_bndrs,body) = collectBinders rhs
+             (body_env, arg_bndrs') = extendBndrsWith RecArg env arg_bndrs
+       ; (body_usg, body') <- scExpr body_env body
+       ; let (rhs_usg, arg_occs) = lookupOccs body_usg arg_bndrs'
+       ; return (rhs_usg, (bndr, arg_bndrs', body', arg_occs)) }
+
+               -- The arg_occs says how the visible,
+               -- lambda-bound binders of the RHS are used
+               -- (including the TyVar binders)
+               -- Two pats are the same if they match both ways

 
 ----------------------
 
 ----------------------

+specInfoBinds :: RhsInfo -> SpecInfo -> [(Id,CoreExpr)]
+specInfoBinds (fn, args, body, _) (SI specs _ _)
+  = [(id,rhs) | OS _ _ id rhs <- specs] ++ 
+    [(fn `addIdSpecialisations` rules, mkLams args body)]
+  where
+    rules = [r | OS _ r _ _ <- specs]
+
+----------------------
+varUsage :: ScEnv -> OutVar -> ArgOcc -> ScUsage

 varUsage env v use 
 varUsage env v use 

-  | Just RecArg <- lookupScopeEnv env v = SCU { calls = emptyVarEnv, 
-                                               occs = unitVarEnv v use }
+  | Just RecArg <- lookupHowBound env v = SCU { scu_calls = emptyVarEnv 
+                                             , scu_occs = unitVarEnv v use }

   | otherwise                          = nullUsage
 \end{code}
 
 
 %************************************************************************
 %*                                                                     *
   | otherwise                          = nullUsage
 \end{code}
 
 
 %************************************************************************
 %*                                                                     *

-\subsection{The specialiser}
+               The specialiser itself

 %*                                                                     *
 %************************************************************************
 
 \begin{code}
 %*                                                                     *
 %************************************************************************
 
 \begin{code}

-specialise :: ScEnv
-          -> Id                        -- Functionn
-          -> [CoreBndr] -> CoreExpr    -- Its RHS
-          -> ScUsage                   -- Info on usage
-          -> UniqSM ([CoreRule],       -- Rules
-                     [(Id,CoreExpr)])  -- Bindings
-
-specialise env fn bndrs body (SCU {calls=calls, occs=occs})
-  = getUs              `thenUs` \ us ->
-    let
-       all_calls = lookupVarEnv calls fn `orElse` []
-
-       good_calls :: [[CoreArg]]
-       good_calls = [ pats
-                    | (con_env, call_args) <- all_calls,
-                      call_args `lengthAtLeast` n_bndrs,           -- App is saturated
-                      let call = bndrs `zip` call_args,
-                      any (good_arg con_env occs) call,    -- At least one arg is a constr app
-                      let (_, pats) = argsToPats con_env us call_args
-                    ]
-    in
-    mapAndUnzipUs (spec_one env fn (mkLams bndrs body)) 
-                 (nubBy same_call good_calls `zip` [1..])
-  where
-    n_bndrs  = length bndrs
-    same_call as1 as2 = and (zipWith tcEqExpr as1 as2)
+type RhsInfo = (OutId, [OutVar], OutExpr, [ArgOcc])
+       -- Info about the *original* RHS of a binding we are specialising
+       -- Original binding f = \xs.body
+       -- Plus info about usage of arguments
+
+data SpecInfo = SI [OneSpec]           -- The specialisations we have generated
+                  Int                  -- Length of specs; used for numbering them
+                  (Maybe ScUsage)      -- Nothing => we have generated specialisations
+                                       --            from calls in the *original* RHS
+                                       -- Just cs => we haven't, and this is the usage
+                                       --            of the original RHS
+
+       -- One specialisation: Rule plus definition
+data OneSpec  = OS CallPat             -- Call pattern that generated this specialisation
+                  CoreRule             -- Rule connecting original id with the specialisation
+                  OutId OutExpr        -- Spec id + its rhs
+
+
+specLoop :: ScEnv
+        -> CallEnv
+        -> [RhsInfo]
+        -> ScUsage -> [SpecInfo]               -- One per binder; acccumulating parameter
+        -> UniqSM (ScUsage, [SpecInfo])        -- ...ditto...
+specLoop env all_calls rhs_infos usg_so_far specs_so_far
+  = do { specs_w_usg <- zipWithM (specialise env all_calls) rhs_infos specs_so_far
+       ; let (new_usg_s, all_specs) = unzip specs_w_usg
+             new_usg   = combineUsages new_usg_s
+             new_calls = scu_calls new_usg
+             all_usg   = usg_so_far `combineUsage` new_usg
+       ; if isEmptyVarEnv new_calls then
+               return (all_usg, all_specs) 
+         else 
+               specLoop env new_calls rhs_infos all_usg all_specs }
+
+specialise 
+   :: ScEnv
+   -> CallEnv                          -- Info on calls
+   -> RhsInfo
+   -> SpecInfo                         -- Original RHS plus patterns dealt with
+   -> UniqSM (ScUsage, SpecInfo)       -- New specialised versions and their usage
+
+-- Note: the rhs here is the optimised version of the original rhs
+-- So when we make a specialised copy of the RHS, we're starting
+-- from an RHS whose nested functions have been optimised already.
+
+specialise env bind_calls (fn, arg_bndrs, body, arg_occs) 
+                         spec_info@(SI specs spec_count mb_unspec)
+  | notNull arg_bndrs, -- Only specialise functions
+    Just all_calls <- lookupVarEnv bind_calls fn
+  = do { (boring_call, pats) <- callsToPats env specs arg_occs all_calls
+--     ; pprTrace "specialise" (vcat [ppr fn <+> ppr arg_occs,
+--                                     text "calls" <+> ppr all_calls,
+--                                     text "good pats" <+> ppr pats])  $
+--       return ()
+
+               -- Bale out if too many specialisations
+               -- Rather a hacky way to do so, but it'll do for now
+       ; let spec_count' = length pats + spec_count
+       ; case sc_count env of
+           Just max | spec_count' > max
+               -> WARN( True, msg ) return (nullUsage, spec_info)
+               where
+                  msg = vcat [ sep [ ptext (sLit "SpecConstr: specialisation of") <+> quotes (ppr fn)
+                                   , nest 2 (ptext (sLit "limited by bound of")) <+> int max ]
+                             , ptext (sLit "Use -fspec-constr-count=n to set the bound")
+                             , extra ]
+                  extra | not opt_PprStyle_Debug = ptext (sLit "Use -dppr-debug to see specialisations")
+                        | otherwise = ptext (sLit "Specialisations:") <+> ppr (pats ++ [p | OS p _ _ _ <- specs])
+
+           _normal_case -> do {
+
+         (spec_usgs, new_specs) <- mapAndUnzipM (spec_one env fn arg_bndrs body)
+                                                (pats `zip` [spec_count..])
+
+       ; let spec_usg = combineUsages spec_usgs
+             (new_usg, mb_unspec')
+                 = case mb_unspec of
+                     Just rhs_usg | boring_call -> (spec_usg `combineUsage` rhs_usg, Nothing)
+                     _                          -> (spec_usg,                      mb_unspec)
+           
+       ; return (new_usg, SI (new_specs ++ specs) spec_count' mb_unspec') } }
+  | otherwise
+  = return (nullUsage, spec_info)              -- The boring case

 
 

----------------------
-good_arg :: ConstrEnv -> IdEnv ArgOcc -> (CoreBndr, CoreArg) -> Bool
--- See Note [Good arguments] above
-good_arg con_env arg_occs (bndr, arg)
-  = case is_con_app_maybe con_env arg of       
-       Just _ ->  bndr_usg_ok arg_occs bndr arg
-       other   -> False
-
-bndr_usg_ok :: IdEnv ArgOcc -> Var -> CoreArg -> Bool
-bndr_usg_ok arg_occs bndr arg
-  = case lookupVarEnv arg_occs bndr of
-       Just CaseScrut -> True                  -- Used only by case scrutiny
-       Just Both      -> case arg of           -- Used by case and elsewhere
-                           App _ _ -> True     -- so the arg should be an explicit con app
-                           other   -> False
-       other -> False                          -- Not used, or used wonkily
-    

 
 ---------------------
 spec_one :: ScEnv
 
 ---------------------
 spec_one :: ScEnv

-        -> Id                                  -- Function
-        -> CoreExpr                            -- Rhs of the original function
-        -> ([CoreArg], Int)
-        -> UniqSM (CoreRule, (Id,CoreExpr))    -- Rule and binding
+        -> OutId       -- Function
+        -> [Var]       -- Lambda-binders of RHS; should match patterns
+        -> CoreExpr    -- Body of the original function
+        -> (CallPat, Int)
+        -> UniqSM (ScUsage, OneSpec)   -- Rule and binding

 
 -- spec_one creates a specialised copy of the function, together
 -- with a rule for using it.  I'm very proud of how short this
 
 -- spec_one creates a specialised copy of the function, together
 -- with a rule for using it.  I'm very proud of how short this

@@ -732,7 +1064,8 @@ spec_one :: ScEnv
          [c::*, v::(b,c) are presumably bound by the (...) part]
   ==>
      f_spec = /\ b c \ v::(b,c) hw::[(a,(b,c))] ->
          [c::*, v::(b,c) are presumably bound by the (...) part]
   ==>
      f_spec = /\ b c \ v::(b,c) hw::[(a,(b,c))] ->

-                 (...entire RHS of f...) (b,c) ((:) (a,(b,c)) (x,v) hw)
+                 (...entire body of f...) [b -> (b,c), 
+                                           y -> ((:) (a,(b,c)) (x,v) hw)]

   
      RULE:  forall b::* c::*,          -- Note, *not* forall a, x
                   v::(b,c),
   
      RULE:  forall b::* c::*,          -- Note, *not* forall a, x
                   v::(b,c),

@@ -741,35 +1074,32 @@ spec_one :: ScEnv
            f (b,c) ((:) (a,(b,c)) (x,v) hw) = f_spec b c v hw
 -}
 
            f (b,c) ((:) (a,(b,c)) (x,v) hw) = f_spec b c v hw
 -}
 

-spec_one env fn rhs (pats, rule_number)
-  = getUniqueUs                `thenUs` \ spec_uniq ->
-    let 
-       fn_name      = idName fn
-       fn_loc       = nameSrcLoc fn_name
-       spec_occ     = mkSpecOcc (nameOccName fn_name)
-       pat_fvs      = varSetElems (exprsFreeVars pats)
-       vars_to_bind = filter not_avail pat_fvs
-               -- See Note [Shadowing] at the top
-
-       not_avail v  = not (v `elemVarEnv` scope env)
-               -- Put the type variables first; the type of a term
-               -- variable may mention a type variable
-       (tvs, ids)   = partition isTyVar vars_to_bind
-       bndrs        = tvs ++ ids
-       spec_body    = mkApps rhs pats
-       body_ty      = exprType spec_body
-       
-       (spec_lam_args, spec_call_args) = mkWorkerArgs bndrs body_ty
-               -- Usual w/w hack to avoid generating 
-               -- a spec_rhs of unlifted type and no args
+spec_one env fn arg_bndrs body (call_pat@(qvars, pats), rule_number)
+  = do {       -- Specialise the body
+         let spec_env = extendScSubstList (extendScInScope env qvars)
+                                          (arg_bndrs `zip` pats)
+       ; (spec_usg, spec_body) <- scExpr spec_env body
+
+--     ; pprTrace "spec_one" (ppr fn <+> vcat [text "pats" <+> ppr pats,
+--                     text "calls" <+> (ppr (scu_calls spec_usg))])
+--       (return ())
+
+               -- And build the results
+       ; spec_uniq <- getUniqueUs
+       ; let (spec_lam_args, spec_call_args) = mkWorkerArgs qvars body_ty
+               -- Usual w/w hack to avoid generating 
+               -- a spec_rhs of unlifted type and no args

        
        

-       rule_name = mkFastString ("SC:" ++ showSDoc (ppr fn <> int rule_number))
-       spec_rhs  = mkLams spec_lam_args spec_body
-       spec_id   = mkUserLocal spec_occ spec_uniq (mkPiTypes spec_lam_args body_ty) fn_loc
-       rule_rhs  = mkVarApps (Var spec_id) spec_call_args
-       rule      = mkLocalRule rule_name specConstrActivation fn_name bndrs pats rule_rhs
-    in
-    returnUs (rule, (spec_id, spec_rhs))
+             fn_name   = idName fn
+             fn_loc    = nameSrcSpan fn_name
+             spec_occ  = mkSpecOcc (nameOccName fn_name)
+             rule_name = mkFastString ("SC:" ++ showSDoc (ppr fn <> int rule_number))
+             spec_rhs  = mkLams spec_lam_args spec_body
+             spec_id   = mkUserLocal spec_occ spec_uniq (mkPiTypes spec_lam_args body_ty) fn_loc
+             body_ty   = exprType spec_body
+             rule_rhs  = mkVarApps (Var spec_id) spec_call_args
+             rule      = mkLocalRule rule_name specConstrActivation fn_name qvars pats rule_rhs
+       ; return (spec_usg, OS call_pat rule spec_id spec_rhs) }

 
 -- In which phase should the specialise-constructor rules be active?
 -- Originally I made them always-active, but Manuel found that
 
 -- In which phase should the specialise-constructor rules be active?
 -- Originally I made them always-active, but Manuel found that

@@ -792,68 +1122,262 @@ specConstrActivation = ActiveAfter 0    -- Baked in; see comments above
 This code deals with analysing call-site arguments to see whether
 they are constructor applications.
 
 This code deals with analysing call-site arguments to see whether
 they are constructor applications.
 

+

 \begin{code}
 \begin{code}

+type CallPat = ([Var], [CoreExpr])     -- Quantified variables and arguments
+
+
+callsToPats :: ScEnv -> [OneSpec] -> [ArgOcc] -> [Call] -> UniqSM (Bool, [CallPat])
+       -- Result has no duplicate patterns, 
+       -- nor ones mentioned in done_pats
+       -- Bool indicates that there was at least one boring pattern
+callsToPats env done_specs bndr_occs calls
+  = do { mb_pats <- mapM (callToPats env bndr_occs) calls
+
+       ; let good_pats :: [([Var], [CoreArg])]
+             good_pats = catMaybes mb_pats
+             done_pats = [p | OS p _ _ _ <- done_specs] 
+             is_done p = any (samePat p) done_pats
+
+       ; return (any isNothing mb_pats, 
+                 filterOut is_done (nubBy samePat good_pats)) }
+
+callToPats :: ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
+       -- The [Var] is the variables to quantify over in the rule
+       --      Type variables come first, since they may scope 
+       --      over the following term variables
+       -- The [CoreExpr] are the argument patterns for the rule
+callToPats env bndr_occs (con_env, args)
+  | length args < length bndr_occs     -- Check saturated
+  = return Nothing
+  | otherwise
+  = do { let in_scope = substInScope (sc_subst env)
+       ; prs <- argsToPats in_scope con_env (args `zip` bndr_occs)
+       ; let (interesting_s, pats) = unzip prs
+             pat_fvs = varSetElems (exprsFreeVars pats)
+             qvars   = filterOut (`elemInScopeSet` in_scope) pat_fvs
+               -- Quantify over variables that are not in sccpe
+               -- at the call site
+               -- See Note [Shadowing] at the top
+               
+             (tvs, ids) = partition isTyVar qvars
+             qvars'     = tvs ++ ids
+               -- Put the type variables first; the type of a term
+               -- variable may mention a type variable
+
+       ; -- pprTrace "callToPats"  (ppr args $$ ppr prs $$ ppr bndr_occs) $
+         if or interesting_s
+         then return (Just (qvars', pats))
+         else return Nothing }
+

     -- argToPat takes an actual argument, and returns an abstracted
     -- version, consisting of just the "constructor skeleton" of the
     -- argument, with non-constructor sub-expression replaced by new
     -- placeholder variables.  For example:
     --    C a (D (f x) (g y))  ==>  C p1 (D p2 p3)
 
     -- argToPat takes an actual argument, and returns an abstracted
     -- version, consisting of just the "constructor skeleton" of the
     -- argument, with non-constructor sub-expression replaced by new
     -- placeholder variables.  For example:
     --    C a (D (f x) (g y))  ==>  C p1 (D p2 p3)
 

-argToPat   :: ConstrEnv -> UniqSupply -> CoreArg -> (UniqSupply, CoreExpr)
-argToPat env us (Type ty) 
-  = (us, Type ty)
-
-argToPat env us arg
-  | Just (CV dc args) <- is_con_app_maybe env arg
-  = let
-       (us',args') = argsToPats env us args
-    in
-    (us', mk_con_app dc args')
-
-argToPat env us (Var v)        -- Don't uniqify existing vars,
-  = (us, Var v)                -- so that we can spot when we pass them twice
-
-argToPat env us arg
-  = (us1, Var (mkSysLocal FSLIT("sc") (uniqFromSupply us2) (exprType arg)))
+argToPat :: InScopeSet                 -- What's in scope at the fn defn site
+        -> ValueEnv                    -- ValueEnv at the call site
+        -> CoreArg                     -- A call arg (or component thereof)
+        -> ArgOcc
+        -> UniqSM (Bool, CoreArg)
+-- Returns (interesting, pat), 
+-- where pat is the pattern derived from the argument
+--           intersting=True if the pattern is non-trivial (not a variable or type)
+-- E.g.                x:xs         --> (True, x:xs)
+--             f xs         --> (False, w)        where w is a fresh wildcard
+--             (f xs, 'c')  --> (True, (w, 'c'))  where w is a fresh wildcard
+--             \x. x+y      --> (True, \x. x+y)
+--             lvl7         --> (True, lvl7)      if lvl7 is bound 
+--                                                somewhere further out
+
+argToPat _in_scope _val_env arg@(Type {}) _arg_occ
+  = return (False, arg)
+
+argToPat in_scope val_env (Note _ arg) arg_occ
+  = argToPat in_scope val_env arg arg_occ
+       -- Note [Notes in call patterns]
+       -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+       -- Ignore Notes.  In particular, we want to ignore any InlineMe notes
+       -- Perhaps we should not ignore profiling notes, but I'm going to
+       -- ride roughshod over them all for now.
+       --- See Note [Notes in RULE matching] in Rules
+
+argToPat in_scope val_env (Let _ arg) arg_occ
+  = argToPat in_scope val_env arg arg_occ
+       -- Look through let expressions
+       -- e.g.         f (let v = rhs in \y -> ...v...)
+       -- Here we can specialise for f (\y -> ...)
+       -- because the rule-matcher will look through the let.
+
+argToPat in_scope val_env (Cast arg co) arg_occ
+  = do { (interesting, arg') <- argToPat in_scope val_env arg arg_occ
+       ; let (ty1,ty2) = coercionKind co
+       ; if not interesting then 
+               wildCardPat ty2
+         else do
+       { -- Make a wild-card pattern for the coercion
+         uniq <- getUniqueUs
+       ; let co_name = mkSysTvName uniq (fsLit "sg")
+             co_var = mkCoVar co_name (mkCoKind ty1 ty2)
+       ; return (interesting, Cast arg' (mkTyVarTy co_var)) } }
+
+{-     Disabling lambda specialisation for now
+       It's fragile, and the spec_loop can be infinite
+argToPat in_scope val_env arg arg_occ
+  | is_value_lam arg
+  = return (True, arg)

   where
   where

-    (us1,us2) = splitUniqSupply us
+    is_value_lam (Lam v e)     -- Spot a value lambda, even if 
+       | isId v = True         -- it is inside a type lambda
+       | otherwise = is_value_lam e
+    is_value_lam other = False
+-}

 
 

-argsToPats :: ConstrEnv -> UniqSupply -> [CoreArg] -> (UniqSupply, [CoreExpr])
-argsToPats env us args = mapAccumL (argToPat env) us args
+  -- Check for a constructor application
+  -- NB: this *precedes* the Var case, so that we catch nullary constrs
+argToPat in_scope val_env arg arg_occ
+  | Just (ConVal dc args) <- isValue val_env arg
+  , case arg_occ of
+       ScrutOcc _ -> True              -- Used only by case scrutinee
+       BothOcc    -> case arg of       -- Used elsewhere
+                       App {} -> True  --     see Note [Reboxing]
+                       _other -> False
+       _other     -> False     -- No point; the arg is not decomposed
+  = do { args' <- argsToPats in_scope val_env (args `zip` conArgOccs arg_occ dc)
+       ; return (True, mk_con_app dc (map snd args')) }
+
+  -- Check if the argument is a variable that 
+  -- is in scope at the function definition site
+  -- It's worth specialising on this if
+  --   (a) it's used in an interesting way in the body
+  --   (b) we know what its value is
+argToPat in_scope val_env (Var v) arg_occ
+  | case arg_occ of { UnkOcc -> False; _other -> True },       -- (a)
+    is_value                                                   -- (b)
+  = return (True, Var v)
+  where
+    is_value 
+       | isLocalId v = v `elemInScopeSet` in_scope 
+                       && isJust (lookupVarEnv val_env v)
+               -- Local variables have values in val_env
+       | otherwise   = isValueUnfolding (idUnfolding v)
+               -- Imports have unfoldings
+
+--     I'm really not sure what this comment means
+--     And by not wild-carding we tend to get forall'd 
+--     variables that are in soope, which in turn can
+--     expose the weakness in let-matching
+--     See Note [Matching lets] in Rules
+
+  -- Check for a variable bound inside the function. 
+  -- Don't make a wild-card, because we may usefully share
+  --   e.g.  f a = let x = ... in f (x,x)
+  -- NB: this case follows the lambda and con-app cases!!
+-- argToPat _in_scope _val_env (Var v) _arg_occ
+--   = return (False, Var v)
+       -- SLPJ : disabling this to avoid proliferation of versions
+       -- also works badly when thinking about seeding the loop
+       -- from the body of the let
+       --       f x y = letrec g z = ... in g (x,y)
+       -- We don't want to specialise for that *particular* x,y
+
+  -- The default case: make a wild-card
+argToPat _in_scope _val_env arg _arg_occ
+  = wildCardPat (exprType arg)
+
+wildCardPat :: Type -> UniqSM (Bool, CoreArg)
+wildCardPat ty = do { uniq <- getUniqueUs
+                   ; let id = mkSysLocal (fsLit "sc") uniq ty
+                   ; return (False, Var id) }
+
+argsToPats :: InScopeSet -> ValueEnv
+          -> [(CoreArg, ArgOcc)]
+          -> UniqSM [(Bool, CoreArg)]
+argsToPats in_scope val_env args
+  = mapM do_one args
+  where
+    do_one (arg,occ) = argToPat in_scope val_env arg occ

 \end{code}
 
 
 \begin{code}
 \end{code}
 
 
 \begin{code}

-is_con_app_maybe :: ConstrEnv -> CoreExpr -> Maybe ConValue
-is_con_app_maybe env (Var v)
-  = case lookupVarEnv env v of
-       Just stuff -> Just stuff
-               -- You might think we could look in the idUnfolding here
+isValue :: ValueEnv -> CoreExpr -> Maybe Value
+isValue _env (Lit lit)
+  = Just (ConVal (LitAlt lit) [])
+
+isValue env (Var v)
+  | Just stuff <- lookupVarEnv env v
+  = Just stuff -- You might think we could look in the idUnfolding here

                -- but that doesn't take account of which branch of a 
                -- case we are in, which is the whole point
 
                -- but that doesn't take account of which branch of a 
                -- case we are in, which is the whole point
 

-       Nothing | isCheapUnfolding unf
-               -> is_con_app_maybe env (unfoldingTemplate unf)
-               where
-                 unf = idUnfolding v
-               -- However we do want to consult the unfolding as well,
-               -- for let-bound constructors!
+  | not (isLocalId v) && isCheapUnfolding unf
+  = isValue env (unfoldingTemplate unf)
+  where
+    unf = idUnfolding v
+       -- However we do want to consult the unfolding 
+       -- as well, for let-bound constructors!

 
 

-       other  -> Nothing
+isValue env (Lam b e)
+  | isTyVar b = case isValue env e of
+                 Just _  -> Just LambdaVal
+                 Nothing -> Nothing
+  | otherwise = Just LambdaVal

 
 

-is_con_app_maybe env (Lit lit)
-  = Just (CV (LitAlt lit) [])
+isValue _env expr      -- Maybe it's a constructor application
+  | (Var fun, args) <- collectArgs expr
+  = case isDataConWorkId_maybe fun of

 
 

-is_con_app_maybe env expr
-  = case collectArgs expr of
-       (Var fun, args) | Just con <- isDataConWorkId_maybe fun,
-                         args `lengthAtLeast` dataConRepArity con
-               -- Might be > because the arity excludes type args
-                       -> Just (CV (DataAlt con) args)
+       Just con | args `lengthAtLeast` dataConRepArity con 
+               -- Check saturated; might be > because the 
+               --                  arity excludes type args
+               -> Just (ConVal (DataAlt con) args)

 
 

-       other -> Nothing
+       _other | valArgCount args < idArity fun
+               -- Under-applied function
+              -> Just LambdaVal        -- Partial application
+
+       _other -> Nothing
+
+isValue _env _expr = Nothing

 
 mk_con_app :: AltCon -> [CoreArg] -> CoreExpr
 mk_con_app (LitAlt lit)  []   = Lit lit
 mk_con_app (DataAlt con) args = mkConApp con args
 
 mk_con_app :: AltCon -> [CoreArg] -> CoreExpr
 mk_con_app (LitAlt lit)  []   = Lit lit
 mk_con_app (DataAlt con) args = mkConApp con args

+mk_con_app _other _args = panic "SpecConstr.mk_con_app"
+
+samePat :: CallPat -> CallPat -> Bool
+samePat (vs1, as1) (vs2, as2)
+  = all2 same as1 as2
+  where
+    same (Var v1) (Var v2) 
+       | v1 `elem` vs1 = v2 `elem` vs2
+       | v2 `elem` vs2 = False
+       | otherwise     = v1 == v2
+
+    same (Lit l1)    (Lit l2)    = l1==l2
+    same (App f1 a1) (App f2 a2) = same f1 f2 && same a1 a2
+
+    same (Type {}) (Type {}) = True    -- Note [Ignore type differences]
+    same (Note _ e1) e2        = same e1 e2    -- Ignore casts and notes
+    same (Cast e1 _) e2        = same e1 e2
+    same e1 (Note _ e2) = same e1 e2
+    same e1 (Cast e2 _) = same e1 e2
+
+    same e1 e2 = WARN( bad e1 || bad e2, ppr e1 $$ ppr e2) 
+                False  -- Let, lambda, case should not occur
+    bad (Case {}) = True
+    bad (Let {})  = True
+    bad (Lam {})  = True
+    bad _other   = False

 \end{code}
 \end{code}

+
+Note [Ignore type differences]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We do not want to generate specialisations where the call patterns
+differ only in their type arguments!  Not only is it utterly useless,
+but it also means that (with polymorphic recursion) we can generate
+an infinite number of specialisations. Example is Data.Sequence.adjustTree, 
+I think.
+