Improve the handling of default methods

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

diff --git a/compiler/coreSyn/CoreSyn.lhs b/compiler/coreSyn/CoreSyn.lhs
index 5c7cef9..83692a8 100644 (file)
--- a/compiler/coreSyn/CoreSyn.lhs
+++ b/compiler/coreSyn/CoreSyn.lhs
@@ -43,7 +43,7 @@ module CoreSyn (
         unSaturatedOk, needSaturated, boringCxtOk, boringCxtNotOk,
        
        -- ** Predicates and deconstruction on 'Unfolding'
-       unfoldingTemplate, setUnfoldingTemplate,
+       unfoldingTemplate, setUnfoldingTemplate, expandUnfolding_maybe,
        maybeUnfoldingTemplate, otherCons, unfoldingArity,
        isValueUnfolding, isEvaldUnfolding, isCheapUnfolding,
         isExpandableUnfolding, isConLikeUnfolding, isCompulsoryUnfolding,
@@ -474,6 +474,7 @@ data UnfoldingGuidance
                 -- See Note [INLINE for small functions] in CoreUnfold
       ug_unsat_ok  :: Bool,    -- True <=> ok to inline even if unsaturated
       ug_boring_ok :: Bool      -- True <=> ok to inline even if the context is boring
+               -- So True,True means "always"
     }
 
   | UnfIfGoodArgs {    -- Arose from a normal Id; the info here is the
@@ -583,6 +584,13 @@ isExpandableUnfolding :: Unfolding -> Bool
 isExpandableUnfolding (CoreUnfolding { uf_expandable = is_expable }) = is_expable
 isExpandableUnfolding _                                              = False
 
+expandUnfolding_maybe :: Unfolding -> Maybe CoreExpr
+-- Expand an expandable unfolding; this is used in rule matching 
+--   See Note [Expanding variables] in Rules.lhs
+-- The key point here is that CONLIKE things can be expanded
+expandUnfolding_maybe (CoreUnfolding { uf_expandable = True, uf_tmpl = rhs }) = Just rhs
+expandUnfolding_maybe _                                                       = Nothing
+
 isInlineRule :: Unfolding -> Bool
 isInlineRule (CoreUnfolding { uf_src = src }) = isInlineRuleSource src
 isInlineRule _                               = False
@@ -638,11 +646,13 @@ When you say
 you intend that calls (f e) are replaced by <rhs>[e/x] So we
 should capture (\x.<rhs>) in the Unfolding of 'f', and never meddle
 with it.  Meanwhile, we can optimise <rhs> to our heart's content,
-leaving the original unfolding intact in Unfolding of 'f'.
+leaving the original unfolding intact in Unfolding of 'f'. For example
+       all xs = foldr (&&) True xs
+       any p = all . map p  {-# INLINE any #-}
+We optimise any's RHS fully, but leave the InlineRule saying "all . map p",
+which deforests well at the call site.
 
-So the representation of an Unfolding has changed quite a bit
-(see CoreSyn).  An INLINE pragma gives rise to an InlineRule 
-unfolding.  
+So INLINE pragma gives rise to an InlineRule, which captures the original RHS.
 
 Moreover, it's only used when 'f' is applied to the
 specified number of arguments; that is, the number of argument on