Make SpecConstr more informative output when there are too many specialisations

It now says something like

  SpecConstr
    Function `happyDoAction'
      has 17 call pattterns, but the limit is 3
    Use -fspec-constr-count=n to set the bound
    Use -dppr-debug to see specialisations

Previously it just silently did no specialisation

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index b95b903..ade88d9 100644 (file)
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -1097,20 +1097,24 @@ specialise env force_spec bind_calls (fn, arg_bndrs, body, arg_occs)
   , notNull arg_bndrs          -- Only specialise functions
   , Just all_calls <- lookupVarEnv bind_calls fn
   = do { (boring_call, pats) <- callsToPats env specs arg_occs all_calls
---     ; pprTrace "specialise" (vcat [ppr fn <+> ppr arg_occs,
---                                     text "calls" <+> ppr all_calls,
---                                     text "good pats" <+> ppr pats])  $
+--     ; pprTrace "specialise" (vcat [ ppr fn <+> text "with" <+> int (length pats) <+> text "good patterns"
+--                                      , text "arg_occs" <+> ppr arg_occs,
+--                                   , text "calls" <+> ppr all_calls,
+--                                   , text "good pats" <+> ppr pats])  $
 --       return ()
 
                -- Bale out if too many specialisations
                -- Rather a hacky way to do so, but it'll do for now
-       ; let spec_count' = length pats + spec_count
+       ; let n_pats = length pats
+              spec_count' = length pats + spec_count
        ; case sc_count env of
            Just max | not force_spec && spec_count' > max
-               -> WARN( True, msg ) return (nullUsage, spec_info)
+               -> pprTrace "SpecConstr" msg $  
+                  return (nullUsage, spec_info)
                where
-                  msg = vcat [ sep [ ptext (sLit "SpecConstr: specialisation of") <+> quotes (ppr fn)
-                                   , nest 2 (ptext (sLit "limited by bound of")) <+> int max ]
+                  msg = vcat [ sep [ ptext (sLit "Function") <+> quotes (ppr fn)
+                                   , nest 2 (ptext (sLit "has") <+> int n_pats <+> 
+                                              ptext (sLit "call pattterns, but the limit is") <+> int max) ]
                              , ptext (sLit "Use -fspec-constr-count=n to set the bound")
                              , extra ]
                   extra | not opt_PprStyle_Debug = ptext (sLit "Use -dppr-debug to see specialisations")