new simpler GC

1 files changed, 53 insertions, 0 deletions

diff --git a/src/value.c b/src/value.c
index 07af689..b4e22a9 100644
--- a/src/value.c
+++ b/src/value.c
@@ -1,5 +1,11 @@
 #include "value.h"
 #include "gc.h"
+#include "util.h"
+#include <inttypes.h>
+
+static const intptr_t FIXNUM_MIN = -((intptr_t)1 << (4 * sizeof(void *) - 3)),
+                      FIXNUM_MAX =
+                          ((intptr_t)1 << (4 * sizeof(void *) - 3)) - 1;
 
 enum builtin {
   BUILTIN_BUILTIN_CLASS_BIGNUM,
@@ -83,6 +89,8 @@ static struct value pop(void) { return (struct value){.bits = 0}; }
 
 struct value alloc_builtin_object(struct value class, size_t value_slot_count,
                                   size_t untraced_slot_count) {
+  assume(value_slot_count != 0);
+
   struct object *obj;
   if (class.bits == builtins[BUILTIN_BUILTIN_CLASS_COMPILED_FUNCTION].bits)
     obj = gc_alloc_compiled_function(value_slot_count, untraced_slot_count);
@@ -96,6 +104,51 @@ struct value alloc_builtin_object(struct value class, size_t value_slot_count,
   };
 }
 
+struct value integer_of_int(intptr_t n) {
+  if (FIXNUM_MIN <= n && n <= FIXNUM_MAX) {
+    struct value value = (struct value){.bits = (n << 2) | TAG_FIXNUM};
+    assume(untag_fixnum(value) == n);
+    return value;
+  } else {
+    todo("integer_of_int: bigint %" PRIdPTR, n);
+  }
+}
+
+enum value_tag get_tag(struct value value) {
+  uintptr_t low_bits = value.bits & 0b111;
+  switch (low_bits) {
+  case 0b000:
+  case 0b010:
+  case 0b100:
+  case 0b110:
+    return (enum value_tag)low_bits;
+  case 0b001:
+  case 0b101:
+    return TAG_FIXNUM;
+  default:
+    unreachable("invalid tag for value %p", (void *)value.bits);
+  }
+}
+
+bool is_ptr(struct value value) { return !(value.bits & 1); }
+
+struct value tag_ptr(struct object *obj, enum value_tag tag) {
+  assume((tag & 0b1) == 0);
+  assume(((uintptr_t)obj & 0b111) == 0);
+  return (struct value){.bits = (uintptr_t)obj | tag};
+}
+
+intptr_t untag_fixnum(struct value value) {
+  assume(get_tag(value) == TAG_FIXNUM);
+  intptr_t bits = value.bits;
+  return bits >> 2;
+}
+
+struct object *untag_ptr(struct value value) {
+  assume(is_ptr(value));
+  return (struct object *)((uintptr_t)value.bits & ~0b111);
+}
+
 void bootstrap(void) {
   // Since it is its own class, standard-class needs to be constructed
   // manually.