1 files changed, 55 insertions, 1 deletions

diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 20f100b427..d99f6548f9 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -919,8 +919,9 @@ do {							\
 #define EQUEUE_ISEMPTY(q) (q.back == q.front && q.possibly_empty)
 
 #define EQUEUE_GET(q) ({				\
+    UWord x;						\
     q.possibly_empty = 1;				\
-    UWord x = *(q.front);				\
+    x = *(q.front);					\
     if (++(q.front) == q.end) {				\
         q.front = q.start;				\
     }							\
@@ -1035,11 +1036,64 @@ __decl_noreturn void __noreturn erl_exit(int n, char*, ...);
 __decl_noreturn void __noreturn erl_exit_flush_async(int n, char*, ...);
 void erl_error(char*, va_list);
 
+/* This controls whether sharing-preserving copy is used by Erlang */
+
+#define SHCOPY_SEND
+#define SHCOPY_SPAWN
+
+#if defined(SHCOPY_SEND) \
+ || defined(SHCOPY_SPAWN)
+#define SHCOPY
+/* Use this with care, it is *very* verbose! */
+#undef SHCOPY_DEBUG
+#endif
+
+#define VERBOSE_DEBUG(...) do {		\
+    erts_fprintf(stderr, __VA_ARGS__);	\
+  } while(0)
+
+#define ERTS_SHCOPY_FLG_MASK	(((unsigned) 3) << 0)
+#define ERTS_SHCOPY_FLG_NONE	(((unsigned) 1) << 0)
+#define ERTS_SHCOPY_FLG_TMP_BUF	(((unsigned) 1) << 1)
+
+/* The persistent state while the sharing-preserving copier works */
+
+typedef struct shcopy_info {
+    Eterm  queue_default[DEF_EQUEUE_SIZE];
+    Eterm* queue_start;
+    Eterm* queue_end;
+    ErtsAlcType_t queue_alloc_type;
+    UWord  bitstore_default[DEF_WSTACK_SIZE];
+    UWord* bitstore_start;
+    ErtsAlcType_t bitstore_alloc_type;
+    Eterm  shtable_default[DEF_ESTACK_SIZE];
+    Eterm* shtable_start;
+    ErtsAlcType_t shtable_alloc_type;
+} shcopy_info;
+
+#define DESTROY_INFO(info)						\
+do {									\
+    if (info.queue_start != info.queue_default) {			\
+	erts_free(info.queue_alloc_type, info.queue_start);		\
+    }									\
+    if (info.bitstore_start != info.bitstore_default) {			\
+	erts_free(info.bitstore_alloc_type, info.bitstore_start);	\
+    }									\
+    if (info.shtable_start != info.shtable_default) {			\
+	erts_free(info.shtable_alloc_type, info.shtable_start);		\
+    }									\
+} while(0)
+
 /* copy.c */
 Eterm copy_object_x(Eterm, Process*, Uint);
 #define copy_object(Term, Proc) copy_object_x(Term,Proc,0)
 
 Uint size_object(Eterm);
+Uint copy_shared_calculate(Eterm, shcopy_info*, unsigned);
+Eterm copy_shared_perform(Eterm, Uint, shcopy_info*, Eterm**, ErlOffHeap*, unsigned);
+
+Uint size_shared(Eterm);
+
 Eterm copy_struct(Eterm, Uint, Eterm**, ErlOffHeap*);
 Eterm copy_shallow(Eterm*, Uint, Eterm**, ErlOffHeap*);