Port to aarch64 (ARM 8).

Continuations don't work yet.

* gc.c (STACK_TOP_EXTRA_WORDS): New macro.
(mark): On aarch64, we must include four words above
the stack top. Some live root pointers sometimes
hide there which are not in any of the callee-saved register
that end up in the machine context via jmp_save.

* jmp.S (jmp_save, jmp_restore): Implement for aarch64.

1 files changed, 7 insertions, 1 deletions

diff --git a/gc.c b/gc.c
index d8f8b1ff..3ec20d76 100644
--- a/gc.c
+++ b/gc.c
@@ -52,6 +52,12 @@
 #define FRESHOBJ_VEC_SIZE       (8 * HEAP_SIZE)
 #define DFL_MALLOC_DELTA_THRESH (64L * 1024 * 1024)
 
+#if __aarch64__
+#define STACK_TOP_EXTRA_WORDS 4
+#else
+#define STACK_TOP_EXTRA_WORDS 0
+#endif
+
 typedef struct heap {
   struct heap *next;
   obj_t block[HEAP_SIZE];
@@ -499,7 +505,7 @@ static void mark(mach_context_t *pmc, val *gc_stack_top)
   /*
    * Finally, the stack.
    */
-  mark_mem_region(gc_stack_top, gc_stack_bottom);
+  mark_mem_region(gc_stack_top - STACK_TOP_EXTRA_WORDS, gc_stack_bottom);
 }
 
 static int sweep_one(obj_t *block)