X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=96857a38edabe31662b10114675bae6fc2996173;hb=f2e74c8829d283aab5024731506f505ec4d5c7cb;hp=4a8ad544a9767c17872f9a28d6f3e4d1d0c9c182;hpb=b8ee6f14ca6e9e49015ee9b404cf8b8191fede05;p=ghc-hetmet.git

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 4a8ad54..96857a3 100644
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -475,9 +475,9 @@ On the other hand, it is bad not to do ANY inlining into an
 InlineRule, because then recursive knots in instance declarations
 don't get unravelled.
 
-However, *sometimes* SimplGently must do no call-site inlining at all.
-Before full laziness we must be careful not to inline wrappers,
-because doing so inhibits floating
+However, *sometimes* SimplGently must do no call-site inlining at all
+(hence sm_inline = False).  Before full laziness we must be careful
+not to inline wrappers, because doing so inhibits floating
     e.g. ...(case f x of ...)...
     ==> ...(case (case x of I# x# -> fw x#) of ...)...
     ==> ...(case x of I# x# -> case fw x# of ...)...
@@ -502,6 +502,9 @@ RULES are enabled when doing "gentle" simplification.  Two reasons:
     to work in Template Haskell when simplifying
     splices, so we get simpler code for literal strings
 
+But watch out: list fusion can prevent floating.  So use phase control
+to switch off those rules until after floating.
+
 Note [Simplifying inside InlineRules]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 We must take care with simplification inside InlineRules (which come from
@@ -697,6 +700,27 @@ let-float if you inline windowToViewport
 However, as usual for Gentle mode, do not inline things that are
 inactive in the intial stages.  See Note [Gentle mode].
 
+Note [InlineRule and preInlineUnconditionally]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Surprisingly, do not pre-inline-unconditionally Ids with INLINE pragmas!
+Example
+
+   {-# INLINE f #-}
+   f :: Eq a => a -> a
+   f x = ...
+   
+   fInt :: Int -> Int
+   fInt = f Int dEqInt
+
+   ...fInt...fInt...fInt...
+
+Here f occurs just once, in the RHS of f1. But if we inline it there
+we'll lose the opportunity to inline at each of fInt's call sites.
+The INLINE pragma will only inline when the application is saturated
+for exactly this reason; and we don't want PreInlineUnconditionally
+to second-guess it.  A live example is Trac #3736.
+    c.f. Note [InlineRule and postInlineUnconditionally]
+
 Note [Top-level botomming Ids]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Don't inline top-level Ids that are bottoming, even if they are used just
@@ -707,6 +731,7 @@ Inlining them won't make the program run faster!
 preInlineUnconditionally :: SimplEnv -> TopLevelFlag -> InId -> InExpr -> Bool
 preInlineUnconditionally env top_lvl bndr rhs
   | not active 		                     = False
+  | isStableUnfolding (idUnfolding bndr)     = False    -- Note [InlineRule and preInlineUnconditionally]
   | isTopLevel top_lvl && isBottomingId bndr = False	-- Note [Top-level bottoming Ids]
   | opt_SimplNoPreInlining                   = False
   | otherwise = case idOccInfo bndr of
@@ -971,6 +996,8 @@ Then there's a danger we'll optimise to
 and now postInlineUnconditionally, losing the InlineRule on f.  Now f'
 won't inline because 'e' is too big.
 
+    c.f. Note [InlineRule and preInlineUnconditionally]
+
 
 %************************************************************************
 %*									*
@@ -986,7 +1013,7 @@ mkLam :: SimplEnv -> [OutBndr] -> OutExpr -> SimplM OutExpr
 
 mkLam _b [] body 
   = return body
-mkLam env bndrs body
+mkLam _env bndrs body
   = do	{ dflags <- getDOptsSmpl
 	; mkLam' dflags bndrs body }
   where
@@ -1000,6 +1027,11 @@ mkLam env bndrs body
 	co_vars  = tyVarsOfType co
 	bad bndr = isCoVar bndr && bndr `elemVarSet` co_vars      
 
+    mkLam' dflags bndrs body@(Lam {})
+      = mkLam' dflags (bndrs ++ bndrs1) body1
+      where
+        (bndrs1, body1) = collectBinders body
+
     mkLam' dflags bndrs body
       | dopt Opt_DoEtaReduction dflags,
         Just etad_lam <- tryEtaReduce bndrs body
@@ -1007,9 +1039,7 @@ mkLam env bndrs body
 	   ; return etad_lam }
 
       | dopt Opt_DoLambdaEtaExpansion dflags,
-        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
+   	not (all isTyVar bndrs) -- Don't eta expand type abstractions
       = do { let body' = tryEtaExpansion dflags body
  	   ; return (mkLams bndrs body') }