Completely new treatment of INLINE pragmas (big patch)

[ghc-hetmet.git] / compiler / simplCore / SimplUtils.lhs

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 6739aaf..53c9149 100644 (file)
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -4,26 +4,19 @@
 \section[SimplUtils]{The simplifier utilities}
 
 \begin{code}
 \section[SimplUtils]{The simplifier utilities}
 
 \begin{code}

-{-# OPTIONS -w #-}
--- 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 SimplUtils (
        -- Rebuilding
        mkLam, mkCase, prepareAlts, bindCaseBndr,
 
        -- Inlining,
        preInlineUnconditionally, postInlineUnconditionally, 
 module SimplUtils (
        -- Rebuilding
        mkLam, mkCase, prepareAlts, bindCaseBndr,
 
        -- Inlining,
        preInlineUnconditionally, postInlineUnconditionally, 

-       activeInline, activeRule, inlineMode,
+       activeInline, activeRule, 

 
        -- The continuation type
 
        -- The continuation type

-       SimplCont(..), DupFlag(..), LetRhsFlag(..), 
+       SimplCont(..), DupFlag(..), ArgInfo(..),

        contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, 
        contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, 

-       countValArgs, countArgs, splitInlineCont,
-       mkBoringStop, mkLazyArgStop, mkRhsStop, contIsRhsOrArg,
+       countValArgs, countArgs, 
+       mkBoringStop, mkLazyArgStop, contIsRhsOrArg,

        interestingCallContext, interestingArgContext,
 
        interestingArg, mkArgInfo,
        interestingCallContext, interestingArgContext,
 
        interestingArg, mkArgInfo,

@@ -41,23 +34,22 @@ import qualified CoreSubst
 import PprCore
 import CoreFVs
 import CoreUtils
 import PprCore
 import CoreFVs
 import CoreUtils

-import Literal 

 import CoreUnfold
 import CoreUnfold

-import MkId

 import Name
 import Id
 import Var     ( isCoVar )
 import NewDemand
 import SimplMonad
 import Type    hiding( substTy )
 import Name
 import Id
 import Var     ( isCoVar )
 import NewDemand
 import SimplMonad
 import Type    hiding( substTy )

+import Coercion ( coercionKind )

 import TyCon
 import TyCon

-import DataCon

 import Unify   ( dataConCannotMatch )
 import VarSet
 import BasicTypes
 import Util
 import MonadUtils
 import Outputable
 import Unify   ( dataConCannotMatch )
 import VarSet
 import BasicTypes
 import Util
 import MonadUtils
 import Outputable

+import FastString

 
 import List( nub )
 \end{code}
 
 import List( nub )
 \end{code}

@@ -92,9 +84,7 @@ Key points:
 \begin{code}
 data SimplCont 
   = Stop               -- An empty context, or hole, []     
 \begin{code}
 data SimplCont 
   = Stop               -- An empty context, or hole, []     

-       OutType         -- Type of the result
-       LetRhsFlag
-       Bool            -- True <=> There is something interesting about
+       CallCtxt        -- True <=> There is something interesting about

                        --          the context, and hence the inliner
                        --          should be a bit keener (see interestingCallContext)
                        -- Specifically:
                        --          the context, and hence the inliner
                        --          should be a bit keener (see interestingCallContext)
                        -- Specifically:

@@ -122,84 +112,96 @@ data SimplCont
        SimplCont       
 
   | StrictArg          -- e C
        SimplCont       
 
   | StrictArg          -- e C

-       OutExpr OutType         -- e and its type
-       (Bool,[Bool])           -- Whether the function at the head of e has rules,
-       SimplCont               --     plus strictness flags for further args
-
-data LetRhsFlag = AnArg                -- It's just an argument not a let RHS
-               | AnRhs         -- It's the RHS of a let (so please float lets out of big lambdas)
-
-instance Outputable LetRhsFlag where
-  ppr AnArg = ptext SLIT("arg")
-  ppr AnRhs = ptext SLIT("rhs")
+       OutExpr                 -- e 
+       CallCtxt                -- Whether *this* argument position is interesting
+       ArgInfo                 -- Whether the function at the head of e has rules, etc
+       SimplCont               --     plus strictness flags for *further* args
+
+data ArgInfo 
+  = ArgInfo {
+       ai_rules :: Bool,       -- Function has rules (recursively)
+                               --      => be keener to inline in all args
+       ai_strs :: [Bool],      -- Strictness of arguments
+                               --   Usually infinite, but if it is finite it guarantees
+                               --   that the function diverges after being given
+                               --   that number of args
+       ai_discs :: [Int]       -- Discounts for arguments; non-zero => be keener to inline
+                               --   Always infinite
+    }

 
 instance Outputable SimplCont where
 
 instance Outputable SimplCont where

-  ppr (Stop ty is_rhs _)            = ptext SLIT("Stop") <> brackets (ppr is_rhs) <+> ppr ty
-  ppr (ApplyTo dup arg se cont)      = ((ptext SLIT("ApplyTo") <+> ppr dup <+> pprParendExpr arg)
+  ppr (Stop interesting)            = ptext (sLit "Stop") <> brackets (ppr interesting)
+  ppr (ApplyTo dup arg _ cont)       = ((ptext (sLit "ApplyTo") <+> ppr dup <+> pprParendExpr arg)

                                          {-  $$ nest 2 (pprSimplEnv se) -}) $$ ppr cont
                                          {-  $$ nest 2 (pprSimplEnv se) -}) $$ ppr cont

-  ppr (StrictBind b _ _ _ cont)      = (ptext SLIT("StrictBind") <+> ppr b) $$ ppr cont
-  ppr (StrictArg f _ _ cont)         = (ptext SLIT("StrictArg") <+> ppr f) $$ ppr cont
-  ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$ 
+  ppr (StrictBind b _ _ _ cont)      = (ptext (sLit "StrictBind") <+> ppr b) $$ ppr cont
+  ppr (StrictArg f _ _ cont)         = (ptext (sLit "StrictArg") <+> ppr f) $$ ppr cont
+  ppr (Select dup bndr alts _ cont)  = (ptext (sLit "Select") <+> ppr dup <+> ppr bndr) $$ 

                                       (nest 4 (ppr alts)) $$ ppr cont 
                                       (nest 4 (ppr alts)) $$ ppr cont 

-  ppr (CoerceIt co cont)            = (ptext SLIT("CoerceIt") <+> ppr co) $$ ppr cont
+  ppr (CoerceIt co cont)            = (ptext (sLit "CoerceIt") <+> ppr co) $$ ppr cont

 
 data DupFlag = OkToDup | NoDup
 
 instance Outputable DupFlag where
 
 data DupFlag = OkToDup | NoDup
 
 instance Outputable DupFlag where

-  ppr OkToDup = ptext SLIT("ok")
-  ppr NoDup   = ptext SLIT("nodup")
+  ppr OkToDup = ptext (sLit "ok")
+  ppr NoDup   = ptext (sLit "nodup")

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

-mkBoringStop :: OutType -> SimplCont
-mkBoringStop ty = Stop ty AnArg False
+mkBoringStop :: SimplCont
+mkBoringStop = Stop BoringCtxt

 
 

-mkLazyArgStop :: OutType -> Bool -> SimplCont
-mkLazyArgStop ty has_rules = Stop ty AnArg has_rules
-
-mkRhsStop :: OutType -> SimplCont
-mkRhsStop ty = Stop ty AnRhs False
+mkLazyArgStop :: CallCtxt -> SimplCont
+mkLazyArgStop cci = Stop cci

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

-contIsRhsOrArg (Stop {})                = True
-contIsRhsOrArg (StrictBind {})          = True
-contIsRhsOrArg (StrictArg {})           = True
-contIsRhsOrArg other            = False
+contIsRhsOrArg :: SimplCont -> Bool
+contIsRhsOrArg (Stop {})       = True
+contIsRhsOrArg (StrictBind {}) = True
+contIsRhsOrArg (StrictArg {})  = True
+contIsRhsOrArg _               = False

 
 -------------------
 contIsDupable :: SimplCont -> Bool
 
 -------------------
 contIsDupable :: SimplCont -> Bool

-contIsDupable (Stop {})                 = True
+contIsDupable (Stop {})                  = True

 contIsDupable (ApplyTo  OkToDup _ _ _)   = True
 contIsDupable (Select   OkToDup _ _ _ _) = True
 contIsDupable (CoerceIt _ cont)          = contIsDupable cont
 contIsDupable (ApplyTo  OkToDup _ _ _)   = True
 contIsDupable (Select   OkToDup _ _ _ _) = True
 contIsDupable (CoerceIt _ cont)          = contIsDupable cont

-contIsDupable other                     = False
+contIsDupable _                          = False

 
 -------------------
 contIsTrivial :: SimplCont -> Bool
 
 -------------------
 contIsTrivial :: SimplCont -> Bool

-contIsTrivial (Stop {})                          = True
+contIsTrivial (Stop {})                   = True

 contIsTrivial (ApplyTo _ (Type _) _ cont) = contIsTrivial cont
 contIsTrivial (ApplyTo _ (Type _) _ cont) = contIsTrivial cont

-contIsTrivial (CoerceIt _ cont)          = contIsTrivial cont
-contIsTrivial other                      = False
+contIsTrivial (CoerceIt _ cont)           = contIsTrivial cont
+contIsTrivial _                           = False

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

-contResultType :: SimplCont -> OutType
-contResultType (Stop to_ty _ _)                 = to_ty
-contResultType (StrictArg _ _ _ cont)   = contResultType cont
-contResultType (StrictBind _ _ _ _ cont) = contResultType cont
-contResultType (ApplyTo _ _ _ cont)     = contResultType cont
-contResultType (CoerceIt _ cont)        = contResultType cont
-contResultType (Select _ _ _ _ cont)    = contResultType cont
+contResultType :: SimplEnv -> OutType -> SimplCont -> OutType
+contResultType env ty cont
+  = go cont ty
+  where
+    subst_ty se ty = substTy (se `setInScope` env) ty
+
+    go (Stop {})                      ty = ty
+    go (CoerceIt co cont)             _  = go cont (snd (coercionKind co))
+    go (StrictBind _ bs body se cont) _  = go cont (subst_ty se (exprType (mkLams bs body)))
+    go (StrictArg fn _ _ cont)        _  = go cont (funResultTy (exprType fn))
+    go (Select _ _ alts se cont)      _  = go cont (subst_ty se (coreAltsType alts))
+    go (ApplyTo _ arg se cont)        ty = go cont (apply_to_arg ty arg se)
+
+    apply_to_arg ty (Type ty_arg) se = applyTy ty (subst_ty se ty_arg)
+    apply_to_arg ty _             _  = funResultTy ty

 
 -------------------
 countValArgs :: SimplCont -> Int
 
 -------------------
 countValArgs :: SimplCont -> Int

-countValArgs (ApplyTo _ (Type ty) se cont) = countValArgs cont
-countValArgs (ApplyTo _ val_arg   se cont) = 1 + countValArgs cont
-countValArgs other                        = 0
+countValArgs (ApplyTo _ (Type _) _ cont) = countValArgs cont
+countValArgs (ApplyTo _ _        _ cont) = 1 + countValArgs cont
+countValArgs _                           = 0

 
 countArgs :: SimplCont -> Int
 
 countArgs :: SimplCont -> Int

-countArgs (ApplyTo _ arg se cont) = 1 + countArgs cont
-countArgs other                          = 0
+countArgs (ApplyTo _ _ _ cont) = 1 + countArgs cont
+countArgs _                    = 0

 
 contArgs :: SimplCont -> ([OutExpr], SimplCont)
 -- Uses substitution to turn each arg into an OutExpr
 
 contArgs :: SimplCont -> ([OutExpr], SimplCont)
 -- Uses substitution to turn each arg into an OutExpr

@@ -212,26 +214,6 @@ dropArgs :: Int -> SimplCont -> SimplCont
 dropArgs 0 cont = cont
 dropArgs n (ApplyTo _ _ _ cont) = dropArgs (n-1) cont
 dropArgs n other               = pprPanic "dropArgs" (ppr n <+> ppr other)
 dropArgs 0 cont = cont
 dropArgs n (ApplyTo _ _ _ cont) = dropArgs (n-1) cont
 dropArgs n other               = pprPanic "dropArgs" (ppr n <+> ppr other)

-
---------------------
-splitInlineCont :: SimplCont -> Maybe (SimplCont, SimplCont)
--- Returns Nothing if the continuation should dissolve an InlineMe Note
--- Return Just (c1,c2) otherwise, 
---     where c1 is the continuation to put inside the InlineMe 
---     and   c2 outside
-
--- Example: (__inline_me__ (/\a. e)) ty
---     Here we want to do the beta-redex without dissolving the InlineMe
--- See test simpl017 (and Trac #1627) for a good example of why this is important
-
-splitInlineCont (ApplyTo dup (Type ty) se c)
-  | Just (c1, c2) <- splitInlineCont c                 = Just (ApplyTo dup (Type ty) se c1, c2)
-splitInlineCont cont@(Stop ty _ _)             = Just (mkBoringStop ty, cont)
-splitInlineCont cont@(StrictBind bndr _ _ se _) = Just (mkBoringStop (substTy se (idType bndr)), cont)
-splitInlineCont cont@(StrictArg _ fun_ty _ _)   = Just (mkBoringStop (funArgTy fun_ty), cont)
-splitInlineCont other                          = Nothing
-       -- NB: the calculation of the type for mkBoringStop is an annoying
-       --     duplication of the same calucation in mkDupableCont

 \end{code}
 
 
 \end{code}
 
 

@@ -259,7 +241,7 @@ interestingArg (Note _ a)    = interestingArg a
 --                        Lit lit -> True
 --                        _       -> False
 
 --                        Lit lit -> True
 --                        _       -> False
 

-interestingArg other            = True
+interestingArg _                 = True

        -- Consider     let x = 3 in f x
        -- The substitution will contain (x -> ContEx 3), and we want to
        -- to say that x is an interesting argument.
        -- Consider     let x = 3 in f x
        -- The substitution will contain (x -> ContEx 3), and we want to
        -- to say that x is an interesting argument.

@@ -304,23 +286,26 @@ default case.
 
 
 \begin{code}
 
 
 \begin{code}

-interestingCallContext :: SimplCont -> CallContInfo
+interestingCallContext :: SimplCont -> CallCtxt

 interestingCallContext cont
   = interesting cont
   where
     interesting (Select _ bndr _ _ _)
 interestingCallContext cont
   = interesting cont
   where
     interesting (Select _ bndr _ _ _)

-       | isDeadBinder bndr       = CaseCont
-       | otherwise               = InterestingCont
+       | isDeadBinder bndr = CaseCtxt
+       | otherwise         = ArgCtxt False 2   -- If the binder is used, this
+                                               -- is like a strict let

                
                

-    interesting (ApplyTo {})      = InterestingCont
-                                               -- Can happen if we have (coerce t (f x)) y
-                                               -- Perhaps True is a bit over-keen, but I've
-                                               -- seen (coerce f) x, where f has an INLINE prag,
-                                               -- So we have to give some motivation for inlining it
-    interesting (StrictArg {})   = InterestingCont
-    interesting (StrictBind {})          = InterestingCont
-    interesting (Stop ty _ yes)   = if yes then InterestingCont else BoringCont
-    interesting (CoerceIt _ cont) = interesting cont
+    interesting (ApplyTo _ arg _ cont)
+       | isTypeArg arg = interesting cont
+       | otherwise     = ValAppCtxt    -- Can happen if we have (f Int |> co) y
+                                       -- If f has an INLINE prag we need to give it some
+                                       -- motivation to inline. See Note [Cast then apply]
+                                       -- in CoreUnfold
+
+    interesting (StrictArg _ cci _ _)  = cci
+    interesting (StrictBind {})                = BoringCtxt
+    interesting (Stop cci)             = cci
+    interesting (CoerceIt _ cont)      = interesting cont

        -- If this call is the arg of a strict function, the context
        -- is a bit interesting.  If we inline here, we may get useful
        -- evaluation information to avoid repeated evals: e.g.
        -- If this call is the arg of a strict function, the context
        -- is a bit interesting.  If we inline here, we may get useful
        -- evaluation information to avoid repeated evals: e.g.

@@ -341,21 +326,29 @@ interestingCallContext cont
 mkArgInfo :: Id
          -> Int        -- Number of value args
          -> SimplCont  -- Context of the cal
 mkArgInfo :: Id
          -> Int        -- Number of value args
          -> SimplCont  -- Context of the cal

-         -> (Bool, [Bool])     -- Arg info
--- The arg info consists of
---  * A Bool indicating if the function has rules (recursively)
---  * A [Bool] indicating strictness for each arg
--- The [Bool] is usually infinite, but if it is finite it 
--- guarantees that the function diverges after being given
--- that number of args
+         -> ArgInfo

 
 mkArgInfo fun n_val_args call_cont
 
 mkArgInfo fun n_val_args call_cont

-  = (interestingArgContext fun call_cont, fun_stricts)
+  | n_val_args < idArity fun           -- Note [Unsaturated functions]
+  = ArgInfo { ai_rules = False
+           , ai_strs = vanilla_stricts 
+           , ai_discs = vanilla_discounts }
+  | otherwise
+  = ArgInfo { ai_rules = interestingArgContext fun call_cont
+           , ai_strs  = add_type_str (idType fun) arg_stricts
+           , ai_discs = arg_discounts }

   where
   where

-    vanilla_stricts, fun_stricts :: [Bool]
+    vanilla_discounts, arg_discounts :: [Int]
+    vanilla_discounts = repeat 0
+    arg_discounts = case idUnfolding fun of
+                       CoreUnfolding {uf_guidance = UnfoldIfGoodArgs {ug_args = discounts}}
+                             -> discounts ++ vanilla_discounts
+                       _     -> vanilla_discounts
+
+    vanilla_stricts, arg_stricts :: [Bool]

     vanilla_stricts  = repeat False
 
     vanilla_stricts  = repeat False
 

-    fun_stricts
+    arg_stricts

       = case splitStrictSig (idNewStrictness fun) of
          (demands, result_info)
                | not (demands `lengthExceeds` n_val_args)
       = case splitStrictSig (idNewStrictness fun) of
          (demands, result_info)
                | not (demands `lengthExceeds` n_val_args)

@@ -370,8 +363,37 @@ mkArgInfo fun n_val_args call_cont
                        map isStrictDmd demands         -- Finite => result is bottom
                   else
                        map isStrictDmd demands ++ vanilla_stricts
                        map isStrictDmd demands         -- Finite => result is bottom
                   else
                        map isStrictDmd demands ++ vanilla_stricts

-
-         other -> vanilla_stricts      -- Not enough args, or no strictness
+              | otherwise
+              -> WARN( True, text "More demands than arity" <+> ppr fun <+> ppr (idArity fun) 
+                               <+> ppr n_val_args <+> ppr demands ) 
+                  vanilla_stricts      -- Not enough args, or no strictness
+
+    add_type_str :: Type -> [Bool] -> [Bool]
+    -- If the function arg types are strict, record that in the 'strictness bits'
+    -- No need to instantiate because unboxed types (which dominate the strict
+    -- types) can't instantiate type variables.
+    -- add_type_str is done repeatedly (for each call); might be better 
+    -- once-for-all in the function
+    -- But beware primops/datacons with no strictness
+    add_type_str _ [] = []
+    add_type_str fun_ty strs           -- Look through foralls
+       | Just (_, fun_ty') <- splitForAllTy_maybe fun_ty       -- Includes coercions
+       = add_type_str fun_ty' strs
+    add_type_str fun_ty (str:strs)     -- Add strict-type info
+       | Just (arg_ty, fun_ty') <- splitFunTy_maybe fun_ty
+       = (str || isStrictType arg_ty) : add_type_str fun_ty' strs
+    add_type_str _ strs
+       = strs
+
+{- Note [Unsaturated functions]
+  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider (test eyeball/inline4)
+       x = a:as
+       y = f x
+where f has arity 2.  Then we do not want to inline 'x', because
+it'll just be floated out again.  Even if f has lots of discounts
+on its first argument -- it must be saturated for these to kick in
+-}

 
 interestingArgContext :: Id -> SimplCont -> Bool
 -- If the argument has form (f x y), where x,y are boring,
 
 interestingArgContext :: Id -> SimplCont -> Bool
 -- If the argument has form (f x y), where x,y are boring,

@@ -394,12 +416,15 @@ interestingArgContext :: Id -> SimplCont -> Bool
 interestingArgContext fn call_cont
   = idHasRules fn || go call_cont
   where
 interestingArgContext fn call_cont
   = idHasRules fn || go call_cont
   where

-    go (Select {})           = False
-    go (ApplyTo {})          = False
-    go (StrictArg {})        = True
-    go (StrictBind {})       = False   -- ??
-    go (CoerceIt _ c)        = go c
-    go (Stop _ _ interesting) = interesting
+    go (Select {})          = False
+    go (ApplyTo {})         = False
+    go (StrictArg _ cci _ _) = interesting cci
+    go (StrictBind {})      = False    -- ??
+    go (CoerceIt _ c)       = go c
+    go (Stop cci)            = interesting cci
+
+    interesting (ArgCtxt rules _) = rules
+    interesting _                 = False

 \end{code}
 
 
 \end{code}
 
 

@@ -419,7 +444,7 @@ settings:
                        (d) Simplifying a GHCi expression or Template 
                                Haskell splice
 
                        (d) Simplifying a GHCi expression or Template 
                                Haskell splice
 

-       SimplPhase n    Used at all other times
+       SimplPhase n _   Used at all other times

 
 The key thing about SimplGently is that it does no call-site inlining.
 Before full laziness we must be careful not to inline wrappers,
 
 The key thing about SimplGently is that it does no call-site inlining.
 Before full laziness we must be careful not to inline wrappers,

@@ -437,13 +462,7 @@ unboxed tuples and suchlike.
 
 INLINE pragmas
 ~~~~~~~~~~~~~~
 
 INLINE pragmas
 ~~~~~~~~~~~~~~

-SimplGently is also used as the mode to simplify inside an InlineMe note.
-
-\begin{code}
-inlineMode :: SimplifierMode
-inlineMode = SimplGently
-\end{code}
-
+We don't simplify inside InlineRules (which come from INLINE pragmas).

 It really is important to switch off inlinings inside such
 expressions.  Consider the following example 
 
 It really is important to switch off inlinings inside such
 expressions.  Consider the following example 
 

@@ -564,12 +583,12 @@ preInlineUnconditionally env top_lvl bndr rhs
   | otherwise = case idOccInfo bndr of
                  IAmDead                    -> True    -- Happens in ((\x.1) v)
                  OneOcc in_lam True int_cxt -> try_once in_lam int_cxt
   | otherwise = case idOccInfo bndr of
                  IAmDead                    -> True    -- Happens in ((\x.1) v)
                  OneOcc in_lam True int_cxt -> try_once in_lam int_cxt

-                 other                      -> False
+                 _                          -> False

   where
     phase = getMode env
     active = case phase of
   where
     phase = getMode env
     active = case phase of

-                  SimplGently  -> isAlwaysActive prag
-                  SimplPhase n -> isActive n prag
+                  SimplGently    -> isAlwaysActive prag
+                  SimplPhase n _ -> isActive n prag

     prag = idInlinePragma bndr
 
     try_once in_lam int_cxt    -- There's one textual occurrence
     prag = idInlinePragma bndr
 
     try_once in_lam int_cxt    -- There's one textual occurrence

@@ -597,14 +616,14 @@ preInlineUnconditionally env top_lvl bndr rhs
        -- canInlineInLam => free vars of rhs are (Once in_lam) or Many,
        -- so substituting rhs inside a lambda doesn't change the occ info.
        -- Sadly, not quite the same as exprIsHNF.
        -- canInlineInLam => free vars of rhs are (Once in_lam) or Many,
        -- so substituting rhs inside a lambda doesn't change the occ info.
        -- Sadly, not quite the same as exprIsHNF.

-    canInlineInLam (Lit l)             = True
+    canInlineInLam (Lit _)             = True

     canInlineInLam (Lam b e)           = isRuntimeVar b || canInlineInLam e
     canInlineInLam (Note _ e)          = canInlineInLam e
     canInlineInLam _                   = False
 
     early_phase = case phase of
     canInlineInLam (Lam b e)           = isRuntimeVar b || canInlineInLam e
     canInlineInLam (Note _ e)          = canInlineInLam e
     canInlineInLam _                   = False
 
     early_phase = case phase of

-                       SimplPhase 0 -> False
-                       other        -> True
+                       SimplPhase 0 _ -> False
+                       _              -> True

 -- If we don't have this early_phase test, consider
 --     x = length [1,2,3]
 -- The full laziness pass carefully floats all the cons cells to
 -- If we don't have this early_phase test, consider
 --     x = length [1,2,3]
 -- The full laziness pass carefully floats all the cons cells to

@@ -660,7 +679,7 @@ postInlineUnconditionally
     -> Bool
 postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
   | not active            = False
     -> Bool
 postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
   | not active            = False

-  | isLoopBreaker occ_info = False     -- If it's a loop-breaker of any kind, dont' inline
+  | isLoopBreaker occ_info = False     -- If it's a loop-breaker of any kind, don't inline

                                        -- because it might be referred to "earlier"
   | isExportedId bndr      = False
   | exprIsTrivial rhs     = True
                                        -- because it might be referred to "earlier"
   | isExportedId bndr      = False
   | exprIsTrivial rhs     = True

@@ -677,7 +696,7 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
        --         True  -> case x of ...
        --         False -> case x of ...
        -- I'm not sure how important this is in practice
        --         True  -> case x of ...
        --         False -> case x of ...
        -- I'm not sure how important this is in practice

-      OneOcc in_lam one_br int_cxt     -- OneOcc => no code-duplication issue
+      OneOcc in_lam _one_br int_cxt    -- OneOcc => no code-duplication issue

        ->     smallEnoughToInline unfolding    -- Small enough to dup
                        -- ToDo: consider discount on smallEnoughToInline if int_cxt is true
                        --
        ->     smallEnoughToInline unfolding    -- Small enough to dup
                        -- ToDo: consider discount on smallEnoughToInline if int_cxt is true
                        --

@@ -708,24 +727,24 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
                        -- Here x isn't mentioned in the RHS, so we don't want to
                        -- create the (dead) let-binding  let x = (a,b) in ...
 
                        -- Here x isn't mentioned in the RHS, so we don't want to
                        -- create the (dead) let-binding  let x = (a,b) in ...
 

-      other -> False
+      _ -> False

 
 -- Here's an example that we don't handle well:
 --     let f = if b then Left (\x.BIG) else Right (\y.BIG)
 --     in \y. ....case f of {...} ....
 -- Here f is used just once, and duplicating the case work is fine (exprIsCheap).
 -- But
 
 -- Here's an example that we don't handle well:
 --     let f = if b then Left (\x.BIG) else Right (\y.BIG)
 --     in \y. ....case f of {...} ....
 -- Here f is used just once, and duplicating the case work is fine (exprIsCheap).
 -- But

--- * We can't preInlineUnconditionally because that woud invalidate
---   the occ info for b.  
--- * We can't postInlineUnconditionally because the RHS is big, and
---   that risks exponential behaviour
--- * We can't call-site inline, because the rhs is big
+--  - We can't preInlineUnconditionally because that woud invalidate
+--    the occ info for b.
+--  - We can't postInlineUnconditionally because the RHS is big, and
+--    that risks exponential behaviour
+--  - We can't call-site inline, because the rhs is big

 -- Alas!
 
   where
     active = case getMode env of
 -- Alas!
 
   where
     active = case getMode env of

-                  SimplGently  -> isAlwaysActive prag
-                  SimplPhase n -> isActive n prag
+                  SimplGently    -> isAlwaysActive prag
+                  SimplPhase n _ -> isActive n prag

     prag = idInlinePragma bndr
 
 activeInline :: SimplEnv -> OutId -> Bool
     prag = idInlinePragma bndr
 
 activeInline :: SimplEnv -> OutId -> Bool

@@ -733,7 +752,7 @@ activeInline env id
   = case getMode env of
       SimplGently -> False
        -- No inlining at all when doing gentle stuff,
   = case getMode env of
       SimplGently -> False
        -- No inlining at all when doing gentle stuff,

-       -- except for local things that occur once
+       -- except for local things that occur once (pre/postInlineUnconditionally)

        -- The reason is that too little clean-up happens if you 
        -- don't inline use-once things.   Also a bit of inlining is *good* for
        -- full laziness; it can expose constant sub-expressions.
        -- The reason is that too little clean-up happens if you 
        -- don't inline use-once things.   Also a bit of inlining is *good* for
        -- full laziness; it can expose constant sub-expressions.

@@ -747,24 +766,24 @@ activeInline env id
        -- and they are now constructed as Compulsory unfoldings (in MkId)
        -- so they'll happen anyway.
 
        -- and they are now constructed as Compulsory unfoldings (in MkId)
        -- so they'll happen anyway.
 

-      SimplPhase n -> isActive n prag
+      SimplPhase n _ -> isActive n prag

   where
     prag = idInlinePragma id
 
 activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool)
 -- Nothing => No rules at all
 activeRule dflags env
   where
     prag = idInlinePragma id
 
 activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool)
 -- Nothing => No rules at all
 activeRule dflags env

-  | not (dopt Opt_RewriteRules dflags)
+  | not (dopt Opt_EnableRewriteRules dflags)

   = Nothing    -- Rewriting is off
   | otherwise
   = case getMode env of
   = Nothing    -- Rewriting is off
   | otherwise
   = case getMode env of

-       SimplGently  -> Just isAlwaysActive
+       SimplGently    -> Just isAlwaysActive

                        -- Used to be Nothing (no rules in gentle mode)
                        -- Main motivation for changing is that I wanted
                        --      lift String ===> ...
                        -- to work in Template Haskell when simplifying
                        -- splices, so we get simpler code for literal strings
                        -- Used to be Nothing (no rules in gentle mode)
                        -- Main motivation for changing is that I wanted
                        --      lift String ===> ...
                        -- to work in Template Haskell when simplifying
                        -- splices, so we get simpler code for literal strings

-       SimplPhase n -> Just (isActive n)
+       SimplPhase n _ -> Just (isActive n)

 \end{code}
 
 
 \end{code}
 
 

@@ -891,22 +910,33 @@ There are some particularly delicate points here:
 
   So it's important to to the right thing.
 
 
   So it's important to to the right thing.
 

-* We need to be careful if we just look at f's arity. Currently (Dec07),
-  f's arity is visible in its own RHS (see Note [Arity robustness] in 
-  SimplEnv) so we must *not* trust the arity when checking that 'f' is
-  a value.  Instead, look at the unfolding. 
+* Note [Arity care]: we need to be careful if we just look at f's
+  arity. Currently (Dec07), f's arity is visible in its own RHS (see
+  Note [Arity robustness] in SimplEnv) so we must *not* trust the
+  arity when checking that 'f' is a value.  Otherwise we will
+  eta-reduce
+      f = \x. f x
+  to
+      f = f
+  Which might change a terminiating program (think (f `seq` e)) to a 
+  non-terminating one.  So we check for being a loop breaker first.

 
   However for GlobalIds we can look at the arity; and for primops we
   must, since they have no unfolding.  
 
 
   However for GlobalIds we can look at the arity; and for primops we
   must, since they have no unfolding.  
 

-* Regardless of whether 'f' is a vlaue, we always want to 
+* Regardless of whether 'f' is a value, we always want to 

   reduce (/\a -> f a) to f
   This came up in a RULE: foldr (build (/\a -> g a))
   reduce (/\a -> f a) to f
   This came up in a RULE: foldr (build (/\a -> g a))

-  did not match           foldr (build (/\b -> ...something complex...))
+  did not match          foldr (build (/\b -> ...something complex...))

   The type checker can insert these eta-expanded versions,
   with both type and dictionary lambdas; hence the slightly 
   ad-hoc isDictId
 
   The type checker can insert these eta-expanded versions,
   with both type and dictionary lambdas; hence the slightly 
   ad-hoc isDictId
 

+* Never *reduce* arity. For example
+      f = \xy. g x y
+  Then if h has arity 1 we don't want to eta-reduce because then
+  f's arity would decrease, and that is bad
+

 These delicacies are why we don't use exprIsTrivial and exprIsHNF here.
 Alas.
 
 These delicacies are why we don't use exprIsTrivial and exprIsHNF here.
 Alas.
 

@@ -915,6 +945,8 @@ tryEtaReduce :: [OutBndr] -> OutExpr -> Maybe OutExpr
 tryEtaReduce bndrs body 
   = go (reverse bndrs) body
   where
 tryEtaReduce bndrs body 
   = go (reverse bndrs) body
   where

+    incoming_arity = count isId bndrs
+

     go (b : bs) (App fun arg) | ok_arg b arg = go bs fun       -- Loop round
     go []       fun           | ok_fun fun   = Just fun                -- Success!
     go _        _                           = Nothing          -- Failure!
     go (b : bs) (App fun arg) | ok_arg b arg = go bs fun       -- Loop round
     go []       fun           | ok_fun fun   = Just fun                -- Success!
     go _        _                           = Nothing          -- Failure!

@@ -928,10 +960,11 @@ tryEtaReduce bndrs body
        && (ok_fun_id fun_id || all ok_lam bndrs)
     ok_fun _fun = False
 
        && (ok_fun_id fun_id || all ok_lam bndrs)
     ok_fun _fun = False
 

-    ok_fun_id fun
-       | isLocalId fun       = isEvaldUnfolding (idUnfolding fun)
-       | isDataConWorkId fun = True
-       | isGlobalId fun      = idArity fun > 0
+    ok_fun_id fun = fun_arity fun >= incoming_arity
+
+    fun_arity fun            -- See Note [Arity care]
+       | isLocalId fun && isLoopBreaker (idOccInfo fun) = 0
+       | otherwise = idArity fun             

 
     ok_lam v = isTyVar v || isDictId v
 
 
     ok_lam v = isTyVar v || isDictId v
 

@@ -998,7 +1031,7 @@ Consider this:
 We'd like to float this to 
        y1 = /\a. e1
        y2 = /\a. e2
 We'd like to float this to 
        y1 = /\a. e1
        y2 = /\a. e2

-       x = /\a. C (y1 a) (y2 a)
+       x  = /\a. C (y1 a) (y2 a)

 for the usual reasons: we want to inline x rather vigorously.
 
 You may think that this kind of thing is rare.  But in some programs it is
 for the usual reasons: we want to inline x rather vigorously.
 
 You may think that this kind of thing is rare.  But in some programs it is

@@ -1132,7 +1165,8 @@ abstractFloats main_tvs body_env body
       = do { uniq <- getUniqueM
           ; let  poly_name = setNameUnique (idName var) uniq           -- Keep same name
                  poly_ty   = mkForAllTys tvs_here (idType var) -- But new type of course
       = do { uniq <- getUniqueM
           ; let  poly_name = setNameUnique (idName var) uniq           -- Keep same name
                  poly_ty   = mkForAllTys tvs_here (idType var) -- But new type of course

-                 poly_id   = mkLocalId poly_name poly_ty 
+                 poly_id   = transferPolyIdInfo var $  -- Note [transferPolyIdInfo] in Id.lhs
+                             mkLocalId poly_name poly_ty 

           ; return (poly_id, mkTyApps (Var poly_id) (mkTyVarTys tvs_here)) }
                -- In the olden days, it was crucial to copy the occInfo of the original var, 
                -- because we were looking at occurrence-analysed but as yet unsimplified code!
           ; return (poly_id, mkTyApps (Var poly_id) (mkTyVarTys tvs_here)) }
                -- In the olden days, it was crucial to copy the occInfo of the original var, 
                -- because we were looking at occurrence-analysed but as yet unsimplified code!

@@ -1274,12 +1308,12 @@ prepareAlts env scrut case_bndr' alts
 
     imposs_cons = case scrut of
                    Var v -> otherCons (idUnfolding v)
 
     imposs_cons = case scrut of
                    Var v -> otherCons (idUnfolding v)

-                   other -> []
+                   _     -> []

 
     impossible_alt :: CoreAlt -> Bool
     impossible_alt (con, _, _) | con `elem` imposs_cons = True
     impossible_alt (DataAlt con, _, _) = dataConCannotMatch inst_tys con
 
     impossible_alt :: CoreAlt -> Bool
     impossible_alt (con, _, _) | con `elem` imposs_cons = True
     impossible_alt (DataAlt con, _, _) = dataConCannotMatch inst_tys con

-    impossible_alt alt                = False
+    impossible_alt _                   = False

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

@@ -1287,7 +1321,7 @@ prepareAlts env scrut case_bndr' alts
 --------------------------------------------------
 combineIdenticalAlts :: OutId -> [InAlt] -> SimplM [InAlt]
 
 --------------------------------------------------
 combineIdenticalAlts :: OutId -> [InAlt] -> SimplM [InAlt]
 

-combineIdenticalAlts case_bndr alts@((con1,bndrs1,rhs1) : con_alts)
+combineIdenticalAlts case_bndr ((_con1,bndrs1,rhs1) : con_alts)

   | all isDeadBinder bndrs1,                   -- Remember the default 
     length filtered_alts < length con_alts     -- alternative comes first
        -- Also Note [Dead binders]
   | all isDeadBinder bndrs1,                   -- Remember the default 
     length filtered_alts < length con_alts     -- alternative comes first
        -- Also Note [Dead binders]

@@ -1295,9 +1329,9 @@ combineIdenticalAlts case_bndr alts@((con1,bndrs1,rhs1) : con_alts)
        ; return ((DEFAULT, [], rhs1) : filtered_alts) }
   where
     filtered_alts       = filter keep con_alts
        ; return ((DEFAULT, [], rhs1) : filtered_alts) }
   where
     filtered_alts       = filter keep con_alts

-    keep (con,bndrs,rhs) = not (all isDeadBinder bndrs && rhs `cheapEqExpr` rhs1)
+    keep (_con,bndrs,rhs) = not (all isDeadBinder bndrs && rhs `cheapEqExpr` rhs1)

 
 

-combineIdenticalAlts case_bndr alts = return alts
+combineIdenticalAlts _ alts = return alts

 
 -------------------------------------------------------------------------
 --                     Prepare the default alternative
 
 -------------------------------------------------------------------------
 --                     Prepare the default alternative

@@ -1315,7 +1349,7 @@ prepareDefault :: DynFlags
                                        -- And becuase case-merging can cause many to show up
 
 -------        Merge nested cases ----------
                                        -- And becuase case-merging can cause many to show up
 
 -------        Merge nested cases ----------

-prepareDefault dflags env outer_bndr bndr_ty imposs_cons (Just deflt_rhs)
+prepareDefault dflags env outer_bndr _bndr_ty imposs_cons (Just deflt_rhs)

   | dopt Opt_CaseMerge dflags
   , Case (Var inner_scrut_var) inner_bndr _ inner_alts <- deflt_rhs
   , DoneId inner_scrut_var' <- substId env inner_scrut_var
   | dopt Opt_CaseMerge dflags
   , Case (Var inner_scrut_var) inner_bndr _ inner_alts <- deflt_rhs
   , DoneId inner_scrut_var' <- substId env inner_scrut_var

@@ -1347,7 +1381,7 @@ prepareDefault dflags env outer_bndr bndr_ty imposs_cons (Just deflt_rhs)
 
 
 --------- Fill in known constructor -----------
 
 
 --------- Fill in known constructor -----------

-prepareDefault dflags env case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rhs)
+prepareDefault _ _ case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rhs)

   |    -- This branch handles the case where we are 
        -- scrutinisng an algebraic data type
     isAlgTyCon tycon           -- It's a data type, tuple, or unboxed tuples.  
   |    -- This branch handles the case where we are 
        -- scrutinisng an algebraic data type
     isAlgTyCon tycon           -- It's a data type, tuple, or unboxed tuples.  

@@ -1378,13 +1412,18 @@ prepareDefault dflags env case_bndr (Just (tycon, inst_tys)) imposs_cons (Just d
                               dataConRepInstPat us con inst_tys
                     ; return [(DataAlt con, ex_tvs ++ co_tvs ++ arg_ids, deflt_rhs)] }
 
                               dataConRepInstPat us con inst_tys
                     ; return [(DataAlt con, ex_tvs ++ co_tvs ++ arg_ids, deflt_rhs)] }
 

-       two_or_more -> return [(DEFAULT, [], deflt_rhs)]
+       _ -> return [(DEFAULT, [], deflt_rhs)]
+
+  | debugIsOn, isAlgTyCon tycon, not (isOpenTyCon tycon), null (tyConDataCons tycon)
+       -- This can legitimately happen for type families, so don't report that
+  = pprTrace "prepareDefault" (ppr case_bndr <+> ppr tycon)
+        $ return [(DEFAULT, [], deflt_rhs)]

 
 --------- Catch-all cases -----------
 
 --------- Catch-all cases -----------

-prepareDefault dflags env case_bndr bndr_ty imposs_cons (Just deflt_rhs)
+prepareDefault _dflags _env _case_bndr _bndr_ty _imposs_cons (Just deflt_rhs)

   = return [(DEFAULT, [], deflt_rhs)]
 
   = return [(DEFAULT, [], deflt_rhs)]
 

-prepareDefault dflags env case_bndr bndr_ty imposs_cons Nothing
+prepareDefault _dflags _env _case_bndr _bndr_ty _imposs_cons Nothing

   = return []  -- No default branch
 \end{code}
 
   = return []  -- No default branch
 \end{code}
 

@@ -1406,29 +1445,14 @@ mkCase tries these things
 
 
 \begin{code}
 
 
 \begin{code}

-mkCase :: OutExpr -> OutId -> OutType
-       -> [OutAlt]             -- Increasing order
+mkCase :: OutExpr -> OutId -> [OutAlt] -- Increasing order

        -> SimplM OutExpr
 
 --------------------------------------------------
        -> SimplM OutExpr
 
 --------------------------------------------------

---     1. Check for empty alternatives
---------------------------------------------------
-
--- This isn't strictly an error.  It's possible that the simplifer might "see"
--- that an inner case has no accessible alternatives before it "sees" that the
--- entire branch of an outer case is inaccessible.  So we simply
--- put an error case here insteadd
-mkCase scrut case_bndr ty []
-  = pprTrace "mkCase: null alts" (ppr case_bndr <+> ppr scrut) $
-    return (mkApps (Var rUNTIME_ERROR_ID)
-                  [Type ty, Lit (mkStringLit "Impossible alternative")])
-
-
---------------------------------------------------

 --     2. Identity case
 --------------------------------------------------
 
 --     2. Identity case
 --------------------------------------------------
 

-mkCase scrut case_bndr ty alts -- Identity case
+mkCase scrut case_bndr alts    -- Identity case

   | all identity_alt alts
   = do tick (CaseIdentity case_bndr)
        return (re_cast scrut)
   | all identity_alt alts
   = do tick (CaseIdentity case_bndr)
        return (re_cast scrut)

@@ -1439,7 +1463,7 @@ mkCase scrut case_bndr ty alts    -- Identity case
     check_eq (LitAlt lit') _    (Lit lit) = lit == lit'
     check_eq (DataAlt con) args rhs       = rhs `cheapEqExpr` mkConApp con (arg_tys ++ varsToCoreExprs args)
                                         || rhs `cheapEqExpr` Var case_bndr
     check_eq (LitAlt lit') _    (Lit lit) = lit == lit'
     check_eq (DataAlt con) args rhs       = rhs `cheapEqExpr` mkConApp con (arg_tys ++ varsToCoreExprs args)
                                         || rhs `cheapEqExpr` Var case_bndr

-    check_eq con args rhs = False
+    check_eq _ _ _ = False

 
     arg_tys = map Type (tyConAppArgs (idType case_bndr))
 
 
     arg_tys = map Type (tyConAppArgs (idType case_bndr))
 

@@ -1457,14 +1481,14 @@ mkCase scrut case_bndr ty alts  -- Identity case
 
     re_cast scrut = case head alts of
                        (_,_,Cast _ co) -> Cast scrut co
 
     re_cast scrut = case head alts of
                        (_,_,Cast _ co) -> Cast scrut co

-                       other           -> scrut
+                       _               -> scrut

 
 
 
 --------------------------------------------------
 --     Catch-all
 --------------------------------------------------
 
 
 
 --------------------------------------------------
 --     Catch-all
 --------------------------------------------------

-mkCase scrut bndr ty alts = return (Case scrut bndr ty alts)
+mkCase scrut bndr alts = return (Case scrut bndr (coreAltsType alts) alts)

 \end{code}
 
 
 \end{code}
 
 

@@ -1473,7 +1497,8 @@ its dead, because it often is, and occasionally these mkCase transformations
 cascade rather nicely.
 
 \begin{code}
 cascade rather nicely.
 
 \begin{code}

+bindCaseBndr :: Id -> CoreExpr -> CoreExpr -> CoreExpr

 bindCaseBndr bndr rhs body
   | isDeadBinder bndr = body
 bindCaseBndr bndr rhs body
   | isDeadBinder bndr = body

-  | otherwise        = bindNonRec bndr rhs body
+  | otherwise         = bindNonRec bndr rhs body

 \end{code}
 \end{code}