X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fstranal%2FWorkWrap.lhs;h=3667da80837aa889f17c3ebd531ad3fd20e1df16;hb=9fddc2160c524d4fefb9fc8a42704f812aef7bf3;hp=d061de5b8c711a44be5eb0028872068974eb130b;hpb=42b37bc4ee622d3a7745d451da26bf5a14f1e7ea;p=ghc-hetmet.git

diff --git a/compiler/stranal/WorkWrap.lhs b/compiler/stranal/WorkWrap.lhs
index d061de5..3667da8 100644
--- a/compiler/stranal/WorkWrap.lhs
+++ b/compiler/stranal/WorkWrap.lhs
@@ -4,6 +4,13 @@
 \section[WorkWrap]{Worker/wrapper-generating back-end of strictness analyser}
 
 \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 WorkWrap ( wwTopBinds, mkWrapper ) where
 
 #include "HsVersions.h"
@@ -26,7 +33,7 @@ import NewDemand        ( Demand(..), StrictSig(..), DmdType(..), DmdResult(..),
 			)
 import UniqSupply	( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
 import Unique		( hasKey )
-import BasicTypes	( RecFlag(..), isNonRec )
+import BasicTypes	( RecFlag(..), isNonRec, isNeverActive )
 import VarEnv		( isEmptyVarEnv )
 import Maybes		( orElse )
 import DynFlags
@@ -215,6 +222,11 @@ tryWW is_rec fn_id rhs
 	--	fw = \ab -> (__inline (\x -> E)) (a,b)
 	-- and the original __inline now vanishes, so E is no longer
 	-- inside its __inline wrapper.  Death!  Disaster!
+
+  || isNeverActive inline_prag
+	-- No point in worker/wrappering if the thing is never inlined!
+	-- Because the no-inline prag will prevent the wrapper ever
+	-- being inlined at a call site. 
   = returnUs [ (new_fn_id, rhs) ]
 
   | is_thunk && worthSplittingThunk maybe_fn_dmd res_info
@@ -364,17 +376,7 @@ worthSplittingFun ds res
   = any worth_it ds || returnsCPR res
 	-- worthSplitting returns False for an empty list of demands,
 	-- and hence do_strict_ww is False if arity is zero and there is no CPR
-
-	-- We used not to split if the result is bottom.
-	-- [Justification:  there's no efficiency to be gained.]
-	-- But it's sometimes bad not to make a wrapper.  Consider
-	--	fw = \x# -> let x = I# x# in case e of
-	--					p1 -> error_fn x
-	--					p2 -> error_fn x
-	--					p3 -> the real stuff
-	-- The re-boxing code won't go away unless error_fn gets a wrapper too.
-	-- [We don't do reboxing now, but in general it's better to pass 
-	--  an unboxed thing to f, and have it reboxed in the error cases....]
+  -- See Note [Worker-wrapper for bottoming functions]
   where
     worth_it Abs	      = True	-- Absent arg
     worth_it (Eval (Prod ds)) = True	-- Product arg to evaluate
@@ -391,6 +393,19 @@ worthSplittingThunk maybe_dmd res
     worth_it other	   	     = False
 \end{code}
 
+Note [Worker-wrapper for bottoming functions]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We used not to split if the result is bottom.
+[Justification:  there's no efficiency to be gained.]
+
+But it's sometimes bad not to make a wrapper.  Consider
+	fw = \x# -> let x = I# x# in case e of
+					p1 -> error_fn x
+					p2 -> error_fn x
+					p3 -> the real stuff
+The re-boxing code won't go away unless error_fn gets a wrapper too.
+[We don't do reboxing now, but in general it's better to pass an
+unboxed thing to f, and have it reboxed in the error cases....]
 
 
 %************************************************************************