[project @ 2005-11-07 14:43:34 by simonmar]

[ghc-hetmet.git] / ghc / rts / PrimOps.cmm

diff --git a/ghc/rts/PrimOps.cmm b/ghc/rts/PrimOps.cmm
index 1eaf727..630319f 100644 (file)
--- a/ghc/rts/PrimOps.cmm
+++ b/ghc/rts/PrimOps.cmm
@@ -126,21 +126,25 @@ unsafeThawArrayzh_fast
   // the mutable list is not easy, because the mut_list is only singly-linked).
   // 
   // So that we can tell whether a MUT_ARR_PTRS_FROZEN is on the mutable list,
-  // when we freeze it we set the info ptr to be MUT_ARR_PTRS_FROZEN0 to indicate
-  // that it is still on the mutable list.
-
+  // when we freeze it we set the info ptr to be MUT_ARR_PTRS_FROZEN0
+  // to indicate that it is still on the mutable list.
+  //
   // So, when we thaw a MUT_ARR_PTRS_FROZEN, we must cope with two cases:
   // either it is on a mut_list, or it isn't.  We adopt the convention that
   // the closure type is MUT_ARR_PTRS_FROZEN0 if it is on the mutable list,
-  // and MUT_ARR_PTRS_FROZEN otherwise.
+  // and MUT_ARR_PTRS_FROZEN otherwise.  In fact it wouldn't matter if
+  // we put it on the mutable list more than once, but it would get scavenged
+  // multiple times during GC, which would be unnecessarily slow.
   //
-  if (%INFO_TYPE(%GET_STD_INFO(R1)) != HALF_W_(MUT_ARR_PTRS_FROZEN0)) {
+  if (StgHeader_info(R1) != stg_MUT_ARR_PTRS_FROZEN0_info) {
+       SET_INFO(R1,stg_MUT_ARR_PTRS_info);
        foreign "C" recordMutableLock(R1 "ptr") [R1];
+       // must be done after SET_INFO, because it ASSERTs closure_MUTABLE()
+       RET_P(R1);
+  } else {
+       SET_INFO(R1,stg_MUT_ARR_PTRS_info);
+       RET_P(R1);
   }
-
-  SET_INFO(R1,stg_MUT_ARR_PTRS_info);
-
-  RET_P(R1);
 }
 
 /* -----------------------------------------------------------------------------