Comments only

[ghc-hetmet.git] / compiler / basicTypes / BasicTypes.lhs

diff --git a/compiler/basicTypes/BasicTypes.lhs b/compiler/basicTypes/BasicTypes.lhs
index 7a9ff56..cdfc28c 100644 (file)
--- a/compiler/basicTypes/BasicTypes.lhs
+++ b/compiler/basicTypes/BasicTypes.lhs
@@ -58,7 +58,7 @@ module BasicTypes(
 
 #include "HsVersions.h"
 
-import FastString( FastString )
+import FastString
 import Outputable
 \end{code}
 
@@ -378,14 +378,26 @@ data OccInfo
        !OneBranch
        !InterestingCxt
 
-  | IAmALoopBreaker    -- Used by the occurrence analyser to mark loop-breakers
-                       -- in a group of recursive definitions
+  | IAmALoopBreaker    -- Note [LoopBreaker OccInfo]
        !RulesOnly      -- True <=> This is a weak or rules-only loop breaker
-                       --  See OccurAnal Note [Weak loop breakers]
+                       --          See OccurAnal Note [Weak loop breakers]
 
 type RulesOnly = Bool
 \end{code}
 
+Note [LoopBreaker OccInfo]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+An OccInfo of (IAmLoopBreaker False) is used by the occurrence 
+analyser in two ways:
+  (a) to mark loop-breakers in a group of recursive 
+      definitions (hence the name)
+  (b) to mark binders that must not be inlined in this phase
+      (perhaps it has a NOINLINE pragma)
+Things with (IAmLoopBreaker False) do not get an unfolding 
+pinned on to them, so they are completely opaque.
+
+See OccurAnal Note [Weak loop breakers] for (IAmLoopBreaker True).
+
 
 \begin{code}
 isNoOcc :: OccInfo -> Bool