Implement -fexpose-all-unfoldings, and fix a non-termination bug

[ghc-hetmet.git] / compiler / coreSyn / CoreUnfold.lhs

diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs
index fa9f5dc..fd76f23 100644 (file)
--- a/compiler/coreSyn/CoreUnfold.lhs
+++ b/compiler/coreSyn/CoreUnfold.lhs
@@ -93,11 +93,12 @@ mkUnfolding top_lvl expr
        -- Sometimes during simplification, there's a large let-bound thing     
        -- which has been substituted, and so is now dead; so 'expr' contains
        -- two copies of the thing while the occurrence-analysed expression doesn't
-       -- Nevertheless, we don't occ-analyse before computing the size because the
+       -- Nevertheless, we *don't* occ-analyse before computing the size because the
        -- size computation bales out after a while, whereas occurrence analysis does not.
        --
        -- This can occasionally mean that the guidance is very pessimistic;
-       -- it gets fixed up next round
+       -- it gets fixed up next round.  And it should be rare, because large
+       -- let-bound things that are dead are usually caught by preInlineUnconditionally
 
 mkCoreUnfolding :: Bool -> CoreExpr -> Arity -> UnfoldingGuidance -> Unfolding
 -- Occurrence-analyses the expression before capturing it
@@ -121,7 +122,8 @@ mkWwInlineRule id expr arity
 
 mkCompulsoryUnfolding :: CoreExpr -> Unfolding
 mkCompulsoryUnfolding expr        -- Used for things that absolutely must be unfolded
-  = mkCoreUnfolding True expr 0    -- Arity of unfolding doesn't matter
+  = mkCoreUnfolding True expr 
+                    0    -- Arity of unfolding doesn't matter
                     (InlineRule { ir_info = InlAlways, ir_sat = InlUnSat })    
 
 mkInlineRule :: InlSatFlag -> CoreExpr -> Arity -> Unfolding
@@ -190,6 +192,7 @@ Examples
   --------------
     0    42#
     0    x
+    0     True
     2    f x
     1    Just x
     4    f (g x)
@@ -316,9 +319,13 @@ sizeExpr bOMB_OUT_SIZE top_args expr
           _                -> funSize top_args fun (length val_args)
 
     ------------ 
-    size_up_alt (_con, _bndrs, rhs) = size_up rhs
+    size_up_alt (_con, _bndrs, rhs) = size_up rhs `addSizeN` 1
        -- Don't charge for args, so that wrappers look cheap
        -- (See comments about wrappers with Case)
+       --
+       -- IMPORATANT: *do* charge 1 for the alternative, else we 
+       -- find that giant case nests are treated as practically free
+       -- A good example is Foreign.C.Error.errrnoToIOError
 
     ------------
        -- These addSize things have to be here because
@@ -389,7 +396,7 @@ funSize top_args fun n_val_args
 
 conSize :: DataCon -> Int -> ExprSize
 conSize dc n_val_args
-  | n_val_args == 0      = SizeIs (_ILIT(0)) emptyBag (_ILIT(1))
+  | n_val_args == 0      = SizeIs (_ILIT(0)) emptyBag (_ILIT(1))       -- Like variables
   | isUnboxedTupleCon dc = SizeIs (_ILIT(0)) emptyBag (iUnbox n_val_args +# _ILIT(1))
   | otherwise           = SizeIs (_ILIT(1)) emptyBag (iUnbox n_val_args +# _ILIT(1))
        -- Treat a constructors application as size 1, regardless of how
@@ -626,10 +633,7 @@ instance Outputable CallCtxt where
   ppr ValAppCtxt      = ptext (sLit "ValAppCtxt")
 
 callSiteInline dflags active_inline id lone_variable arg_infos cont_info
-  = let
-       n_val_args  = length arg_infos
-    in
-    case idUnfolding id of {
+  = case idUnfolding id of {
        NoUnfolding      -> Nothing ;
        OtherCon _       -> Nothing ;
        DFunUnfolding {} -> Nothing ;   -- Never unfold a DFun
@@ -638,6 +642,8 @@ callSiteInline dflags active_inline id lone_variable arg_infos cont_info
                        -- uf_arity will typically be equal to (idArity id), 
                        -- but may be less for InlineRules
     let
+       n_val_args  = length arg_infos
+
        result | yes_or_no = Just unf_template
               | otherwise = Nothing
 
@@ -1125,7 +1131,9 @@ exprIsConApp_maybe expr
                       analyse rhs args
         where
          is_saturated = count isValArg args == idArity fun
-          unfolding = idUnfolding fun
+          unfolding = idUnfolding fun    -- Does not look through loop breakers
+                   -- ToDo: we *may* look through variables that are NOINLINE
+                   --       in this phase, and that is really not right
 
     analyse _ _ = Nothing