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.

3 files changed, 72 insertions, 2 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)
diff --git a/jmp.S b/jmp.S
index 045f1a89..51563636 100644
--- a/jmp.S
+++ b/jmp.S
@@ -33,7 +33,7 @@ _ ## NAME: ;
 #define DEFUN(NAME) \
 .globl _ ## NAME ; \
 _ ## NAME: ;
-#elif __arm__ && !__thumb__
+#elif (__arm__ && !__thumb__) || __aarch64__
 #define DEFUN(NAME) \
 .text ; \
 .align 4 ; \
@@ -295,6 +295,40 @@ DEFUN(jmp_restore)
   mr    %r3, %r4
   blr
 
+#elif __aarch64__
+
+DEFUN(jmp_save)
+  stp x19, x20, [x0, 0]
+  stp x21, x22, [x0, 16]
+  stp x23, x24, [x0, 32]
+  stp x25, x26, [x0, 48]
+  stp x27, x28, [x0, 64]
+  stp x29, x30, [x0, 80]
+  stp d8, d9, [x0, 96]
+  stp d10, d11, [x0, 112]
+  stp d12, d13, [x0, 128]
+  stp d14, d15, [x0, 144]
+  mov x16, sp
+  str x16, [x0, 160]
+  mov w0, #0
+  ret
+
+DEFUN(jmp_restore)
+  ldp x19, x20, [x0, 0]
+  ldp x21, x22, [x0, 16]
+  ldp x23, x24, [x0, 32]
+  ldp x25, x26, [x0, 48]
+  ldp x27, x28, [x0, 64]
+  ldp x29, x30, [x0, 80]
+  ldp d8, d9, [x0, 96]
+  ldp d10, d11, [x0, 112]
+  ldp d12, d13, [x0, 128]
+  ldp d14, d15, [x0, 144]
+  ldr x16, [x0, 160]
+  mov sp, x16
+  mov w0, w1
+  br x30
+
 #else
 #error port me!
 #endif
diff --git a/signal.h b/signal.h
index 435ce6f6..ec56b9e7 100644
--- a/signal.h
+++ b/signal.h
@@ -127,6 +127,36 @@ struct jmp {
   unsigned long r31;
 };
 
+#elif __aarch64__
+
+struct jmp {
+  unsigned long x19;
+  unsigned long x20;
+  unsigned long x21;
+  unsigned long x22;
+  unsigned long x23;
+  unsigned long x24;
+  unsigned long x25;
+  unsigned long x26;
+  unsigned long x27;
+  unsigned long x28;
+  unsigned long x29;
+  unsigned long x30;
+  unsigned long d8;
+  unsigned long d9;
+  unsigned long d10;
+  unsigned long d11;
+  unsigned long d12;
+  unsigned long d13;
+  unsigned long d14;
+  unsigned long d15;
+  unsigned long x16;
+};
+
+/* Jump buffer contains:
+   x19-x28, x29(fp), x30(lr), (x31)sp, d8-d15.  Other registers are not
+   saved.  */
+
 #else
 #error port me!
 #endif