Wibble to substituting InlWrappers

See Note [Worker inlining] in CoreSubst

diff --git a/compiler/coreSyn/CoreSubst.lhs b/compiler/coreSyn/CoreSubst.lhs
index 14eccc6..b02bc80 100644 (file)
--- a/compiler/coreSyn/CoreSubst.lhs
+++ b/compiler/coreSyn/CoreSubst.lhs
@@ -523,13 +523,11 @@ substUnfolding _ unf = unf        -- NoUnfolding, OtherCon
 
 -------------------
 substInlineRuleInfo :: Subst -> InlineRuleInfo -> InlineRuleInfo
-substInlineRuleInfo subst (InlWrapper wkr)
-  = case lookupIdSubst subst wkr of
-      Var w1 -> InlWrapper w1
-      other  -> WARN( not (exprIsTrivial other), text "CoreSubst.substWorker:" <+> ppr wkr )
-               InlVanilla -- Worker has got substituted away altogether
-                          -- (This can happen if it's trivial, via
-                          --  postInlineUnconditionally, hence only warning)
+substInlineRuleInfo (Subst in_scope ids _) (InlWrapper wkr)
+  | Just (Var w1) <- lookupVarEnv  ids      wkr = InlWrapper w1
+  | Just w1       <- lookupInScope in_scope wkr = InlWrapper w1
+  | otherwise = WARN( True, text "Interesting! CoreSubst.substWorker:" <+> ppr wkr )
+               InlVanilla -- Note [Worker inlining]
 substInlineRuleInfo _ info = info
 
 ------------------
@@ -584,6 +582,18 @@ substVarSet subst fvs
        | otherwise = Type.tyVarsOfType (lookupTvSubst subst fv)
 \end{code}
 
+Note [Worker inlining]
+~~~~~~~~~~~~~~~~~~~~~~
+A worker can get sustituted away entirely.
+       - it might be trivial
+       - it might simply be very small
+We do not treat an InlWrapper as an 'occurrence' in the occurence 
+analyser, so it's possible that the worker is not even in scope any more.
+
+In all all these cases we simply drop the special case, returning to
+InlVanilla.  The WARN is just so I can see if it happens a lot.
+
+
 %************************************************************************
 %*                                                                     *
        The Very Simple Optimiser

diff --git a/compiler/coreSyn/CoreSyn.lhs b/compiler/coreSyn/CoreSyn.lhs
index e9e7f8d..0724630 100644 (file)
--- a/compiler/coreSyn/CoreSyn.lhs
+++ b/compiler/coreSyn/CoreSyn.lhs
@@ -477,6 +477,7 @@ data InlineRuleInfo
 
   | InlWrapper Id   -- This unfolding is a the wrapper in a 
                    --     worker/wrapper split from the strictness analyser
+                   -- The Id is the worker-id
                    -- Used to abbreviate the uf_tmpl in interface files
                    --  which don't need to contain the RHS; 
                    --  it can be derived from the strictness info