The Big INLINE Patch: totally reorganise way that INLINE pragmas work

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

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 097ecd2..c541096 100644 (file)
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -10,14 +10,14 @@ module SimplUtils (
 
        -- Inlining,
        preInlineUnconditionally, postInlineUnconditionally, 
 
        -- Inlining,
        preInlineUnconditionally, postInlineUnconditionally, 

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

 
        -- The continuation type
        SimplCont(..), DupFlag(..), ArgInfo(..),
        contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, 
 
        -- The continuation type
        SimplCont(..), DupFlag(..), ArgInfo(..),
        contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, 

-       countValArgs, countArgs, splitInlineCont,
+       countValArgs, countArgs, 

        mkBoringStop, mkLazyArgStop, contIsRhsOrArg,
        mkBoringStop, mkLazyArgStop, contIsRhsOrArg,

-       interestingCallContext, interestingArgContext,
+       interestingCallContext, 

 
        interestingArg, mkArgInfo,
        
 
        interestingArg, mkArgInfo,
        

@@ -34,6 +34,7 @@ import qualified CoreSubst
 import PprCore
 import CoreFVs
 import CoreUtils
 import PprCore
 import CoreFVs
 import CoreUtils

+import CoreArity       ( etaExpand, exprEtaExpandArity )

 import CoreUnfold
 import Name
 import Id
 import CoreUnfold
 import Name
 import Id

@@ -51,7 +52,7 @@ import MonadUtils
 import Outputable
 import FastString
 
 import Outputable
 import FastString
 

-import List( nub )
+import Data.List

 \end{code}
 
 
 \end{code}
 
 

@@ -112,7 +113,7 @@ data SimplCont
        SimplCont       
 
   | StrictArg          -- e C
        SimplCont       
 
   | StrictArg          -- e C

-       OutExpr                 -- e 
+       OutExpr                 -- e; *always* of form (Var v `App1` e1 .. `App` en)

        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
        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

@@ -214,63 +215,11 @@ 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 {})         = Just (mkBoringStop, cont)
-splitInlineCont cont@(StrictBind {})   = Just (mkBoringStop, cont)
-splitInlineCont cont@(StrictArg  {})   = Just (mkBoringStop, cont)
-splitInlineCont _                      = Nothing
-\end{code}
-
-
-\begin{code}
-interestingArg :: OutExpr -> Bool
-       -- An argument is interesting if it has *some* structure
-       -- We are here trying to avoid unfolding a function that
-       -- is applied only to variables that have no unfolding
-       -- (i.e. they are probably lambda bound): f x y z
-       -- There is little point in inlining f here.
-interestingArg (Var v)          = hasSomeUnfolding (idUnfolding v)
-                                       -- Was: isValueUnfolding (idUnfolding v')
-                                       -- But that seems over-pessimistic
-                                || isDataConWorkId v
-                                       -- This accounts for an argument like
-                                       -- () or [], which is definitely interesting
-interestingArg (Type _)                 = False
-interestingArg (App fn (Type _)) = interestingArg fn
-interestingArg (Note _ a)       = interestingArg a
-
--- Idea (from Sam B); I'm not sure if it's a good idea, so commented out for now
--- interestingArg expr | isUnLiftedType (exprType expr)
---        -- Unlifted args are only ever interesting if we know what they are
---  =                  case expr of
---                        Lit lit -> True
---                        _       -> False
-
-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.
-       -- But consider also (\x. f x y) y
-       -- The substitution will contain (x -> ContEx y), and we want to say
-       -- that x is not interesting (assuming y has no unfolding)

 \end{code}
 
 
 \end{code}
 
 

-Comment about interestingCallContext
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Note [Interesting call context]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 We want to avoid inlining an expression where there can't possibly be
 any gain, such as in an argument position.  Hence, if the continuation
 is interesting (eg. a case scrutinee, application etc.) then we
 We want to avoid inlining an expression where there can't possibly be
 any gain, such as in an argument position.  Hence, if the continuation
 is interesting (eg. a case scrutinee, application etc.) then we

@@ -305,20 +254,21 @@ default case.
 
 \begin{code}
 interestingCallContext :: SimplCont -> CallCtxt
 
 \begin{code}
 interestingCallContext :: SimplCont -> CallCtxt

+-- See Note [Interesting call context]

 interestingCallContext cont
   = interesting cont
   where
 interestingCallContext cont
   = interesting cont
   where

-    interestingCtxt = ArgCtxt False 2  -- Give *some* incentive!
-

     interesting (Select _ bndr _ _ _)
     interesting (Select _ bndr _ _ _)

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

                
                

-    interesting (ApplyTo {})      = interestingCtxt
-                               -- Can happen if we have (coerce t (f x)) y
-                               -- Perhaps interestingCtxt 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 (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 (StrictArg _ cci _ _)  = cci
     interesting (StrictBind {})                = BoringCtxt

@@ -342,24 +292,25 @@ interestingCallContext cont
 
 -------------------
 mkArgInfo :: Id
 
 -------------------
 mkArgInfo :: Id

+         -> [CoreRule] -- Rules for function

          -> Int        -- Number of value args
          -> Int        -- Number of value args

-         -> SimplCont  -- Context of the cal
+         -> SimplCont  -- Context of the call

          -> ArgInfo
 
          -> ArgInfo
 

-mkArgInfo fun n_val_args call_cont
+mkArgInfo fun rules n_val_args call_cont

   | n_val_args < idArity fun           -- Note [Unsaturated functions]
   = ArgInfo { ai_rules = False
            , ai_strs = vanilla_stricts 
            , ai_discs = vanilla_discounts }
   | otherwise
   | 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
+  = ArgInfo { ai_rules = interestingArgContext rules call_cont

            , ai_strs  = add_type_str (idType fun) arg_stricts
            , ai_discs = arg_discounts }
   where
     vanilla_discounts, arg_discounts :: [Int]
     vanilla_discounts = repeat 0
     arg_discounts = case idUnfolding fun of
            , ai_strs  = add_type_str (idType fun) arg_stricts
            , ai_discs = arg_discounts }
   where
     vanilla_discounts, arg_discounts :: [Int]
     vanilla_discounts = repeat 0
     arg_discounts = case idUnfolding fun of

-                       CoreUnfolding _ _ _ _ (UnfoldIfGoodArgs _ discounts _ _)
+                       CoreUnfolding {uf_guidance = UnfoldIfGoodArgs {ug_args = discounts}}

                              -> discounts ++ vanilla_discounts
                        _     -> vanilla_discounts
 
                              -> discounts ++ vanilla_discounts
                        _     -> vanilla_discounts
 

@@ -413,7 +364,7 @@ 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
 -}
 
 on its first argument -- it must be saturated for these to kick in
 -}
 

-interestingArgContext :: Id -> SimplCont -> Bool
+interestingArgContext :: [CoreRule] -> SimplCont -> Bool

 -- If the argument has form (f x y), where x,y are boring,
 -- and f is marked INLINE, then we don't want to inline f.
 -- But if the context of the argument is
 -- If the argument has form (f x y), where x,y are boring,
 -- and f is marked INLINE, then we don't want to inline f.
 -- But if the context of the argument is

@@ -424,16 +375,18 @@ interestingArgContext :: Id -> SimplCont -> Bool
 -- where h has rules, then we do want to inline f; hence the
 -- call_cont argument to interestingArgContext
 --
 -- where h has rules, then we do want to inline f; hence the
 -- call_cont argument to interestingArgContext
 --

--- The interesting_arg_ctxt flag makes this happen; if it's
+-- The ai-rules flag makes this happen; if it's

 -- set, the inliner gets just enough keener to inline f 
 -- regardless of how boring f's arguments are, if it's marked INLINE
 --
 -- The alternative would be to *always* inline an INLINE function,
 -- regardless of how boring its context is; but that seems overkill
 -- For example, it'd mean that wrapper functions were always inlined
 -- set, the inliner gets just enough keener to inline f 
 -- regardless of how boring f's arguments are, if it's marked INLINE
 --
 -- The alternative would be to *always* inline an INLINE function,
 -- regardless of how boring its context is; but that seems overkill
 -- For example, it'd mean that wrapper functions were always inlined

-interestingArgContext fn call_cont
-  = idHasRules fn || go call_cont
+interestingArgContext rules call_cont
+  = notNull rules || enclosing_fn_has_rules

   where
   where

+    enclosing_fn_has_rules = go call_cont
+

     go (Select {})          = False
     go (ApplyTo {})         = False
     go (StrictArg _ cci _ _) = interesting cci
     go (Select {})          = False
     go (ApplyTo {})         = False
     go (StrictArg _ cci _ _) = interesting cci

@@ -480,13 +433,7 @@ 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 
 

@@ -611,9 +558,9 @@ preInlineUnconditionally env top_lvl bndr rhs
   where
     phase = getMode env
     active = case phase of
   where
     phase = getMode env
     active = case phase of

-                  SimplGently    -> isAlwaysActive prag
-                  SimplPhase n _ -> isActive n prag
-    prag = idInlinePragma bndr
+                  SimplGently    -> isEarlyActive act
+                  SimplPhase n _ -> isActive n act
+    act = idInlineActivation bndr

 
     try_once in_lam int_cxt    -- There's one textual occurrence
        | not in_lam = isNotTopLevel top_lvl || early_phase
 
     try_once in_lam int_cxt    -- There's one textual occurrence
        | not in_lam = isNotTopLevel top_lvl || early_phase

@@ -696,7 +643,7 @@ story for now.
 \begin{code}
 postInlineUnconditionally 
     :: SimplEnv -> TopLevelFlag
 \begin{code}
 postInlineUnconditionally 
     :: SimplEnv -> TopLevelFlag

-    -> InId            -- The binder (an OutId would be fine too)
+    -> OutId           -- The binder (an InId would be fine too)

     -> OccInfo                 -- From the InId
     -> OutExpr
     -> Unfolding
     -> OccInfo                 -- From the InId
     -> OutExpr
     -> Unfolding

@@ -706,6 +653,7 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
   | 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
   | 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

+  | isInlineRule unfolding = False     -- Note [InlineRule and postInlineUnconditionally]

   | exprIsTrivial rhs     = True
   | otherwise
   = case occ_info of
   | exprIsTrivial rhs     = True
   | otherwise
   = case occ_info of

@@ -767,9 +715,9 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
 
   where
     active = case getMode env of
 
   where
     active = case getMode env of

-                  SimplGently    -> isAlwaysActive prag
-                  SimplPhase n _ -> isActive n prag
-    prag = idInlinePragma bndr
+                  SimplGently    -> isAlwaysActive act
+                  SimplPhase n _ -> isActive n act
+    act = idInlineActivation bndr

 
 activeInline :: SimplEnv -> OutId -> Bool
 activeInline env id
 
 activeInline :: SimplEnv -> OutId -> Bool
 activeInline env id

@@ -790,9 +738,9 @@ 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 act

   where
   where

-    prag = idInlinePragma id
+    act = idInlineActivation id

 
 activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool)
 -- Nothing => No rules at all
 
 activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool)
 -- Nothing => No rules at all

@@ -810,6 +758,23 @@ activeRule dflags env
        SimplPhase n _ -> Just (isActive n)
 \end{code}
 
        SimplPhase n _ -> Just (isActive n)
 \end{code}
 

+Note [InlineRule and postInlineUnconditionally]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Do not do postInlineUnconditionally if the Id has an InlineRule, otherwise
+we lose the unfolding.  Example
+
+     -- f has InlineRule with rhs (e |> co)
+     --   where 'e' is big
+     f = e |> co
+
+Then there's a danger we'll optimise to
+
+     f' = e
+     f = f' |> co
+
+and now postInlineUnconditionally, losing the InlineRule on f.  Now f'
+won't inline because 'e' is too big.
+

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

@@ -818,14 +783,14 @@ activeRule dflags env
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

-mkLam :: [OutBndr] -> OutExpr -> SimplM OutExpr
+mkLam :: SimplEnv -> [OutBndr] -> OutExpr -> SimplM OutExpr

 -- mkLam tries three things
 --     a) eta reduction, if that gives a trivial expression
 --     b) eta expansion [only if there are some value lambdas]
 
 -- mkLam tries three things
 --     a) eta reduction, if that gives a trivial expression
 --     b) eta expansion [only if there are some value lambdas]
 

-mkLam [] body 
+mkLam _b [] body 

   = return body
   = return body

-mkLam bndrs body
+mkLam env bndrs body

   = do { dflags <- getDOptsSmpl
        ; mkLam' dflags bndrs body }
   where
   = do { dflags <- getDOptsSmpl
        ; mkLam' dflags bndrs body }
   where

@@ -846,8 +811,10 @@ mkLam bndrs body
           ; return etad_lam }
 
       | dopt Opt_DoLambdaEtaExpansion dflags,
           ; return etad_lam }
 
       | dopt Opt_DoLambdaEtaExpansion dflags,

-       any isRuntimeVar bndrs
-      = do { body' <- tryEtaExpansion dflags body
+        not (inGentleMode env),              -- In gentle mode don't eta-expansion
+       any isRuntimeVar bndrs        -- because it can clutter up the code
+                                     -- with casts etc that may not be removed
+      = do { let body' = tryEtaExpansion dflags body

           ; return (mkLams bndrs body') }
    
       | otherwise 
           ; return (mkLams bndrs body') }
    
       | otherwise 

@@ -1032,11 +999,10 @@ when computing arity; and etaExpand adds the coerces as necessary when
 actually computing the expansion.
 
 \begin{code}
 actually computing the expansion.
 
 \begin{code}

-tryEtaExpansion :: DynFlags -> OutExpr -> SimplM OutExpr
+tryEtaExpansion :: DynFlags -> OutExpr -> OutExpr

 -- There is at least one runtime binder in the binders
 -- There is at least one runtime binder in the binders

-tryEtaExpansion dflags body = do
-    us <- getUniquesM
-    return (etaExpand fun_arity us body (exprType body))
+tryEtaExpansion dflags body
+  = etaExpand fun_arity body

   where
     fun_arity = exprEtaExpandArity dflags body
 \end{code}
   where
     fun_arity = exprEtaExpandArity dflags body
 \end{code}

@@ -1189,7 +1155,7 @@ 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   = transferPolyIdInfo var $  -- Note [transferPolyIdInfo] in Id.lhs
+                 poly_id   = transferPolyIdInfo var tvs_here $ -- 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, 
                              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,