X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FbasicTypes%2FBasicTypes.lhs;h=c43280fbd43ef148efff519931ebb1dd736cb6ce;hb=afaceeff37e6347113399f6ec8a61dfcbd22dcac;hp=d73e4f1818d27645bf5e5cdced4d0554949b1cc7;hpb=bf40e268d916947786c56ec38db86190854a2d2c;p=ghc-hetmet.git

diff --git a/compiler/basicTypes/BasicTypes.lhs b/compiler/basicTypes/BasicTypes.lhs
index d73e4f1..c43280f 100644
--- a/compiler/basicTypes/BasicTypes.lhs
+++ b/compiler/basicTypes/BasicTypes.lhs
@@ -38,7 +38,7 @@ module BasicTypes(
 	TupCon(..), tupleParens,
 
 	OccInfo(..), seqOccInfo, isFragileOcc, isOneOcc, 
-	isDeadOcc, isLoopBreaker, isNoOcc,
+	isDeadOcc, isLoopBreaker, isNonRuleLoopBreaker, isNoOcc,
 
 	InsideLam, insideLam, notInsideLam,
 	OneBranch, oneBranch, notOneBranch,
@@ -365,18 +365,28 @@ defn of OccInfo here, safely at the bottom
 
 \begin{code}
 data OccInfo 
-  = NoOccInfo
+  = NoOccInfo		-- Many occurrences, or unknown
 
   | IAmDead		-- Marks unused variables.  Sometimes useful for
 			-- lambda and case-bound variables.
 
-  | OneOcc !InsideLam
- 	   !OneBranch
-	   !InterestingCxt
+  | OneOcc		-- Occurs exactly once, not inside a rule
+	!InsideLam
+ 	!OneBranch
+	!InterestingCxt
 
   | IAmALoopBreaker	-- Used by the occurrence analyser to mark loop-breakers
 			-- in a group of recursive definitions
+	!RulesOnly	-- True <=> This loop breaker mentions the other binders
+			--	    in its recursive group only in its RULES, not
+			--	    in its rhs
+			--  See OccurAnal Note [RulesOnly]
 
+type RulesOnly = Bool
+\end{code}
+
+
+\begin{code}
 isNoOcc :: OccInfo -> Bool
 isNoOcc NoOccInfo = True
 isNoOcc other     = False
@@ -403,8 +413,12 @@ oneBranch    = True
 notOneBranch = False
 
 isLoopBreaker :: OccInfo -> Bool
-isLoopBreaker IAmALoopBreaker = True
-isLoopBreaker other	      = False
+isLoopBreaker (IAmALoopBreaker _) = True
+isLoopBreaker other	          = False
+
+isNonRuleLoopBreaker :: OccInfo -> Bool
+isNonRuleLoopBreaker (IAmALoopBreaker False) = True	-- Loop-breaker that breaks a non-rule cycle
+isNonRuleLoopBreaker other	             = False
 
 isDeadOcc :: OccInfo -> Bool
 isDeadOcc IAmDead = True
@@ -421,9 +435,9 @@ isFragileOcc other	    = False
 \begin{code}
 instance Outputable OccInfo where
   -- only used for debugging; never parsed.  KSW 1999-07
-  ppr NoOccInfo  			  	  = empty
-  ppr IAmALoopBreaker 				  = ptext SLIT("LoopBreaker")
-  ppr IAmDead					  = ptext SLIT("Dead")
+  ppr NoOccInfo  	   = empty
+  ppr (IAmALoopBreaker ro) = ptext SLIT("LoopBreaker") <> if ro then char '!' else empty
+  ppr IAmDead		   = ptext SLIT("Dead")
   ppr (OneOcc inside_lam one_branch int_cxt)
 	= ptext SLIT("Once") <> pp_lam <> pp_br <> pp_args
 	where