[project @ 1997-11-24 21:12:32 by sof]

Stack underflow comment added

diff --git a/ghc/runtime/main/StgUpdate.lhc b/ghc/runtime/main/StgUpdate.lhc
index e5c6690..e91a169 100644 (file)
--- a/ghc/runtime/main/StgUpdate.lhc
+++ b/ghc/runtime/main/StgUpdate.lhc
@@ -674,6 +674,14 @@ STGFUN(PAP_entry)
 
     FB_
 
+      /* Concurrent World:
+        If we come from StackUnderflowEnterNode the old StkO has been
+        nuked and the PAP carries over data from the old StkO.
+        The underflow code must restore RetReg to the right value 
+        because it is not grabbed from the update frame if there is data
+        on one of the two stacks.
+          -- HWL
+      */
     while (AREL(SuA - SpA) == 0 && BREL(SuB - SpB) == 0) {
 #ifdef CONCURRENT
         if (SuB < STKO_BSTK_BOT(StkOReg)) {