Separate and optional size thresholds for SpecConstr and LiberateCase

This patch replaces -fspec-threshold by -fspec-constr-threshold and
-fliberate-case-threshold. The thresholds can be disabled by
-fno-spec-constr-threshold and -fno-liberate-case-threshold.

compiler/main/DynFlags.hs

@@ -301,7 +301,8 @@ data DynFlags = DynFlags {
   maxSimplIterations    :: Int,		-- max simplifier iterations
   ruleCheck		:: Maybe String,
 
-  specThreshold		:: Int,		-- Threshold for function specialisation
+  specConstrThreshold   :: Maybe Int,	-- Threshold for SpecConstr
+  liberateCaseThreshold :: Maybe Int,   -- Threshold for LiberateCase 
 
   stolen_x86_regs	:: Int,		
   cmdlineHcIncludes	:: [String],	-- -#includes
@@ -478,7 +479,8 @@ defaultDynFlags =
 	optLevel		= 0,
 	maxSimplIterations	= 4,
 	ruleCheck		= Nothing,
-	specThreshold		= 200,
+	specConstrThreshold	= Just 200,
+        liberateCaseThreshold   = Just 200,
 	stolen_x86_regs		= 4,
 	cmdlineHcIncludes	= [],
 	importPaths		= ["."],
@@ -1140,9 +1142,14 @@ dynamic_flags = [
   ,  ( "fmax-simplifier-iterations", IntSuffix (\n -> 
 		upd (\dfs -> dfs{ maxSimplIterations = n })) )
 
-	-- liberate-case-threshold is an old flag for '-fspec-threshold'
-  ,  ( "fspec-threshold",          IntSuffix (\n -> upd (\dfs -> dfs{ specThreshold = n })))
-  ,  ( "fliberate-case-threshold", IntSuffix (\n -> upd (\dfs -> dfs{ specThreshold = n })))
+  ,  ( "fspec-constr-threshold",      IntSuffix (\n ->
+                upd (\dfs -> dfs{ specConstrThreshold = Just n })))
+  ,  ( "fno-spec-constr-threshold",   NoArg (
+                upd (\dfs -> dfs{ specConstrThreshold = Nothing })))
+  ,  ( "fliberate-case-threshold",    IntSuffix (\n ->
+                upd (\dfs -> dfs{ liberateCaseThreshold = Just n })))
+  ,  ( "fno-liberate-case-threshold", NoArg (
+                upd (\dfs -> dfs{ liberateCaseThreshold = Nothing })))
 
   ,  ( "frule-check",     SepArg (\s -> upd (\dfs -> dfs{ ruleCheck = Just s })))
   ,  ( "fcontext-stack"	, IntSuffix $ \n -> upd $ \dfs -> dfs{ ctxtStkDepth = n })

compiler/simplCore/LiberateCase.lhs

@@ -195,7 +195,8 @@ libCaseBind env (Rec pairs)
 
     rhs_small_enough (id,rhs)
 	=  idArity id > 0	-- Note [Only functions!]
-	&& couldBeSmallEnoughToInline (bombOutSize env) rhs
+	&& maybe True (\size -> couldBeSmallEnoughToInline size rhs)
+                      (bombOutSize env)
 \end{code}
 
 
@@ -349,7 +350,7 @@ topLevel = 0
 \begin{code}
 data LibCaseEnv
   = LibCaseEnv {
-	lc_size :: Int,		-- Bomb-out size for deciding if
+	lc_size :: Maybe Int,	-- Bomb-out size for deciding if
 				-- potential liberatees are too big.
 				-- (passed in from cmd-line args)
 
@@ -377,7 +378,7 @@ data LibCaseEnv
 
 initEnv :: DynFlags -> LibCaseEnv
 initEnv dflags 
-  = LibCaseEnv { lc_size = specThreshold dflags,
+  = LibCaseEnv { lc_size = liberateCaseThreshold dflags,
 		 lc_lvl = 0,
 		 lc_lvl_env = emptyVarEnv, 
 		 lc_rec_env = emptyVarEnv,

compiler/specialise/SpecConstr.lhs

@@ -456,9 +456,9 @@ specConstrProgram dflags us binds
 %************************************************************************
 
 \begin{code}
-data ScEnv = SCE { sc_size :: Int,	-- Size threshold
+data ScEnv = SCE { sc_size :: Maybe Int,	-- Size threshold
 
-		   sc_subst :: Subst,	-- Current substitution
+		   sc_subst :: Subst,   	-- Current substitution
 
 		   sc_how_bound :: HowBoundEnv,
 			-- Binds interesting non-top-level variables
@@ -491,7 +491,7 @@ instance Outputable Value where
 
 ---------------------
 initScEnv dflags
-  = SCE { sc_size = specThreshold dflags,
+  = SCE { sc_size = specConstrThreshold dflags,
 	  sc_subst = emptySubst, 
 	  sc_how_bound = emptyVarEnv, 
 	  sc_vals = emptyVarEnv }
@@ -824,7 +824,8 @@ scExpr' env e@(App _ _)
 ----------------------
 scBind :: ScEnv -> CoreBind -> UniqSM (ScEnv, ScUsage, CoreBind)
 scBind env (Rec prs)
-  | not (all (couldBeSmallEnoughToInline (sc_size env)) rhss)
+  | Just threshold <- sc_size env
+  , not (all (couldBeSmallEnoughToInline threshold) rhss)
 		-- No specialisation
   = do	{ let (rhs_env,bndrs') = extendRecBndrs env bndrs
 	; (rhs_usgs, rhss') <- mapAndUnzipUs (scExpr rhs_env) rhss