Improve warning for SpecConstr

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index 7eb3529..bdd9a16 100644 (file)
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -36,6 +36,7 @@ import Name
 import OccName         ( mkSpecOcc )
 import ErrUtils                ( dumpIfSet_dyn )
 import DynFlags                ( DynFlags(..), DynFlag(..) )
+import StaticFlags     ( opt_PprStyle_Debug )
 import StaticFlags     ( opt_SpecInlineJoinPoints )
 import BasicTypes      ( Activation(..) )
 import Maybes          ( orElse, catMaybes, isJust, isNothing )
@@ -1021,10 +1022,14 @@ specialise env bind_calls (fn, arg_bndrs, body, arg_occs)
        ; let spec_count' = length pats + spec_count
        ; case sc_count env of
            Just max | spec_count' > max
-               -> pprTrace "SpecConstr: too many specialisations for one function (see -fspec-constr-count):" 
-                        (vcat [ptext (sLit "Function:") <+> ppr fn,
-                               ptext (sLit "Specialisations:") <+> ppr (pats ++ [p | OS p _ _ _ <- specs])])
-                        return (nullUsage, spec_info)
+               -> WARN( True, 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 ]
+                             , 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")
+                        | otherwise = ptext (sLit "Specialisations:") <+> ppr (pats ++ [p | OS p _ _ _ <- specs])
 
            _normal_case -> do {
 

diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs
index 4058a97..db6f96a 100644 (file)
--- a/compiler/utils/Util.lhs
+++ b/compiler/utils/Util.lhs
@@ -107,6 +107,15 @@ infixr 9 `thenCmp`
 %*                                                                      *
 %************************************************************************
 
+These booleans are global constants, set by CPP flags.  They allow us to
+recompile a single module (this one) to change whether or not debug output
+appears. They sometimes let us avoid even running CPP elsewhere.
+
+It's important that the flags are literal constants (True/False). Then,
+with -0, tests of the flags in other modules will simplify to the correct
+branch of the conditional, thereby dropping debug code altogether when
+the flags are off.
+
 \begin{code}
 ghciSupported :: Bool
 #ifdef GHCI