Always expose the unfolding of something with an InlineRule

Previously a bottoming function with a strictness wrapper
had a hidden inlining, and that was Very Bad, because in
    f x = if ... then bot_fun x else x+1
we really want to pass the *unboxed* x to bot_fun. This
happens quite a bit in error handling code, eg for array
indexing.

diff --git a/compiler/main/TidyPgm.lhs b/compiler/main/TidyPgm.lhs
index 41d9234..d8bacd8 100644 (file)
--- a/compiler/main/TidyPgm.lhs
+++ b/compiler/main/TidyPgm.lhs
@@ -686,7 +686,7 @@ addExternal expose_all id = (new_needed_ids, show_unfold)
                        (varSetElems spec_ids) -- XXX non-det ordering
 
     idinfo        = idInfo id
-    dont_inline           = isNeverActive (inlinePragmaActivation (inlinePragInfo idinfo))
+    never_active   = isNeverActive (inlinePragmaActivation (inlinePragInfo idinfo))
     loop_breaker   = isNonRuleLoopBreaker (occInfo idinfo)
     bottoming_fn   = isBottomingSig (strictnessInfo idinfo `orElse` topSig)
     spec_ids      = specInfoFreeVars (specInfo idinfo)
@@ -699,16 +699,23 @@ addExternal expose_all id = (new_needed_ids, show_unfold)
 
     mb_unfold_ids :: Maybe (IdSet, [Id])       -- Nothing => don't unfold
     mb_unfold_ids = case unfoldingInfo idinfo of
-                     CoreUnfolding { uf_tmpl = unf_rhs, uf_guidance = guide } 
-                       | expose_all ||      -- expose_all says to expose all 
-                                            -- unfoldings willy-nilly
-                          not (bottoming_fn     -- No need to inline bottom functions
-                           || dont_inline       -- Or ones that say not to
-                           || loop_breaker      -- Or that are loop breakers
-                           || neverUnfoldGuidance guide)
+                     CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src, uf_guidance = guide } 
+                       | show_unfolding src guide
                        -> Just (exprFvsInOrder unf_rhs)
                      DFunUnfolding _ ops -> Just (exprsFvsInOrder ops)
-                     _ -> Nothing
+                     _                   -> Nothing
+
+    show_unfolding unf_source unf_guidance
+       =  expose_all        -- 'expose_all' says to expose all 
+                            -- unfoldings willy-nilly
+
+       || isInlineRuleSource unf_source             -- Always expose things whose 
+                                                    -- source is an inline rule
+
+       || not (bottoming_fn     -- No need to inline bottom functions
+          || never_active       -- Or ones that say not to
+          || loop_breaker       -- Or that are loop breakers
+          || neverUnfoldGuidance unf_guidance)
 
 -- We want a deterministic free-variable list.  exprFreeVars gives us
 -- a VarSet, which is in a non-deterministic order when converted to a