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 4ddd8ca..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,
        

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

-import List( nub )
+import Data.List

 \end{code}
 
 
 \end{code}
 
 

@@ -215,73 +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 _                      = Nothing
-       -- NB: we dissolve an InlineMe in any strict context, 
-       --     not just function aplication.  
-       -- E.g.  foldr k z (__inline_me (case x of p -> build ...))
-       --     Here we want to get rid of the __inline_me__ so we
-       --     can float the case, and see foldr/build
-       --
-       -- However *not* in a strict RHS, else we get
-       --         let f = __inline_me__ (\x. e) in ...f...
-       -- Now if f is guaranteed to be called, hence a strict binding
-       -- we don't thereby want to dissolve the __inline_me__; for
-       -- example, 'f' might be a  wrapper, so we'd inline the worker
-\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

@@ -316,6 +254,7 @@ 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

@@ -353,24 +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
 

@@ -424,7 +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

@@ -435,16 +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

@@ -491,13 +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 
 

@@ -622,7 +558,7 @@ preInlineUnconditionally env top_lvl bndr rhs
   where
     phase = getMode env
     active = case phase of
   where
     phase = getMode env
     active = case phase of

-                  SimplGently    -> isAlwaysActive act
+                  SimplGently    -> isEarlyActive act

                   SimplPhase n _ -> isActive n act
     act = idInlineActivation bndr
 
                   SimplPhase n _ -> isActive n act
     act = idInlineActivation bndr
 

@@ -707,7 +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

@@ -717,6 +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

@@ -821,6 +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.
+

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

@@ -836,7 +790,7 @@ mkLam :: SimplEnv -> [OutBndr] -> OutExpr -> SimplM OutExpr
 
 mkLam _b [] body 
   = return body
 
 mkLam _b [] body 
   = return body

-mkLam _env bndrs body
+mkLam env bndrs body

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

@@ -857,7 +811,9 @@ mkLam _env bndrs body
           ; return etad_lam }
 
       | dopt Opt_DoLambdaEtaExpansion dflags,
           ; return etad_lam }
 
       | dopt Opt_DoLambdaEtaExpansion dflags,

-       any isRuntimeVar bndrs
+        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') }
    
       = do { let body' = tryEtaExpansion dflags body
           ; return (mkLams bndrs body') }