lisp: INT -> SMI

when we implement big integer support, we should use INT there
instead.  SMI signals intent much better.

include/alisp/lisp.h

@@ -26,48 +26,35 @@ typedef struct
 /// Tagging system
 typedef enum Tag
 {
-  TAG_NIL  = 0b00000000, // Start of atomic types
-  TAG_INT  = 0b00000001, // Special tag so we can encode 63 bit integers
-  TAG_SYM  = 0b00000100,
-  TAG_CONS = 0b00000010, // Start of container types
-  TAG_VEC  = 0b00000110,
+  TAG_SMI  = 0b00000001, // Atomic types
+  TAG_SYM  = 0b00000011,
+  TAG_NIL  = 0b00000000, // Container types (0 LSB)
+  TAG_CONS = 0b00000010,
+  TAG_VEC  = 0b00000100,
   NUM_TAGS = 5,
 } tag_t;
 
-static_assert(NUM_TAGS == 5, "Expected NUM_TAGS == 5 for enum SHIFT");
-enum Shift
-{
-  SHIFT_INT  = 1,
-  SHIFT_SYM  = 8,
-  SHIFT_CONS = 8,
-  SHIFT_VEC  = 8,
-};
-
-static_assert(NUM_TAGS == 5, "Expected NUM_TAGS == 5 for enum MASK");
-enum Mask
-{
-  MASK_INT  = 0b00000001,
-  MASK_SYM  = 0b11111111,
-  MASK_CONS = 0b11111111,
-  MASK_VEC  = 0b11111111,
-};
-
 // Some helper macros for tagging
-#define TAG(PTR, TYPE)    ((lisp_t *)(((PTR) << SHIFT_##TYPE) | TAG_##TYPE))
-#define IS_TAG(PTR, TYPE) (((u64)(PTR) & MASK_##TYPE) == TAG_##TYPE)
-#define UNTAG(PTR, TYPE)  (((u64)PTR) >> SHIFT_##TYPE)
+#define SHIFT_TAG (8)
+#define MASK_TAG  ((1 << SHIFT_TAG) - 1)
 
-#define INT_MAX ((((i64)1) << 62) - 1)
-#define INT_MIN (-(((i64)1) << 62))
+#define TAG(PTR, TYPE)    ((lisp_t *)((((u64)(PTR)) << SHIFT_TAG) | TAG_##TYPE))
+#define UNTAG(PTR)        (((u64)PTR) >> SHIFT_TAG)
+#define GET_TAG(PTR)      ((tag_t)(((u64)(PTR)) & MASK_TAG))
+#define IS_TAG(PTR, TYPE) (GET_TAG(PTR) == TAG_##TYPE)
+
+#define INT_BITS ((sizeof(i64) * 8) - SHIFT_TAG)
+#define INT_MAX  ((((i64)1) << (INT_BITS - 1)) - 1)
+#define INT_MIN  (-(INT_MAX + 1))
 
 tag_t get_tag(const lisp_t *);
-lisp_t *tag_int(const i64);
+lisp_t *tag_smi(const i64);
 lisp_t *tag_sym(const char *);
 lisp_t *tag_cons(const cons_t *);
 lisp_t *tag_vec(const vec_t *);
 lisp_t *tag_generic(void *, tag_t);
 
-i64 as_int(lisp_t *);
+i64 as_smi(lisp_t *);
 char *as_sym(lisp_t *);
 cons_t *as_cons(lisp_t *);
 vec_t *as_vec(lisp_t *);

src/allocator.c

@@ -32,7 +32,7 @@ alloc_node_t *make_node(page_t *page, tag_t type)
     size += sizeof(vec_t);
     break;
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -61,7 +61,7 @@ alloc_node_t *lisp_to_node(lisp_t *lisp)
     raw_ptr = as_vec(lisp);
     break;
   case TAG_NIL: // These shouldn't be allocated
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -80,7 +80,7 @@ lisp_t *alloc_make(alloc_t *alloc, tag_t type)
   case TAG_VEC:
     break;
   case TAG_NIL: // These shouldn't be allocated
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -181,7 +181,7 @@ void alloc_free(alloc_t *alloc)
         vec_free((vec_t *)node->data);
         break;
       case TAG_NIL:
-      case TAG_INT:
+      case TAG_SMI:
       case TAG_SYM:
       default:
         FAIL("Unreachable");

src/lisp.c

@@ -10,24 +10,24 @@
 
 #include <alisp/lisp.h>
 
-lisp_t *tag_int(i64 i)
+lisp_t *tag_smi(i64 i)
 {
-  return TAG((u64)i, INT);
+  return TAG(i, SMI);
 }
 
 lisp_t *tag_sym(const char *str)
 {
-  return TAG((u64)str, SYM);
+  return TAG(str, SYM);
 }
 
 lisp_t *tag_vec(const vec_t *vec)
 {
-  return TAG((u64)vec, VEC);
+  return TAG(vec, VEC);
 }
 
 lisp_t *tag_cons(const cons_t *cons)
 {
-  return TAG((u64)cons, CONS);
+  return TAG(cons, CONS);
 }
 
 lisp_t *tag_generic(void *ptr, tag_t type)
@@ -35,9 +35,9 @@ lisp_t *tag_generic(void *ptr, tag_t type)
   switch (type)
   {
   case TAG_NIL:
-    return NIL;
-  case TAG_INT:
-    return tag_int((i64)ptr);
+    return TAG(ptr, NIL);
+  case TAG_SMI:
+    return tag_smi((i64)ptr);
   case TAG_SYM:
     return tag_sym(ptr);
   case TAG_CONS:
@@ -53,39 +53,34 @@ lisp_t *tag_generic(void *ptr, tag_t type)
 tag_t get_tag(const lisp_t *lisp)
 {
   static_assert(NUM_TAGS == 5);
-  if (!lisp)
-    return TAG_NIL;
-  else if (IS_TAG(lisp, INT))
-    return TAG_INT;
-
-  return (u64)lisp & 0xFF;
+  return GET_TAG(lisp);
 }
 
-i64 as_int(lisp_t *obj)
+i64 as_smi(lisp_t *obj)
 {
-  assert(IS_TAG(obj, INT));
-  u64 p_obj = (u64)obj;
-  return UNTAG(p_obj, INT) |               // Delete the tag
-         (NTH_BYTE(p_obj, 7) & 0x80) << 56 // duplicate the MSB (preserve sign)
-      ;
+  assert(IS_TAG(obj, SMI));
+  u64 raw_obj = UNTAG(obj);
+  u64 msb     = (NTH_BYTE(raw_obj, 6) & 0x80) >> 7;
+  msb         = ((1LU << 8) - msb) << 56;
+  return (i64)(raw_obj | msb);
 }
 
 char *as_sym(lisp_t *obj)
 {
   assert(IS_TAG(obj, SYM));
-  return (char *)UNTAG(obj, SYM);
+  return (char *)UNTAG(obj);
 }
 
 cons_t *as_cons(lisp_t *obj)
 {
   assert(IS_TAG(obj, CONS));
-  return (cons_t *)UNTAG(obj, CONS);
+  return (cons_t *)UNTAG(obj);
 }
 
 vec_t *as_vec(lisp_t *obj)
 {
   assert(IS_TAG(obj, VEC));
-  return (vec_t *)UNTAG(obj, VEC);
+  return (vec_t *)UNTAG(obj);
 }
 
 void lisp_print(FILE *fp, lisp_t *lisp)
@@ -97,11 +92,11 @@ void lisp_print(FILE *fp, lisp_t *lisp)
   case TAG_NIL:
     fprintf(fp, "NIL");
     break;
-  case TAG_INT:
+  case TAG_SMI:
 #if VERBOSE_LOGS == 2
     fprintf(fp, "INT[");
 #endif
-    fprintf(fp, "%ld", as_int(lisp));
+    fprintf(fp, "%ld", as_smi(lisp));
 #if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #endif
@@ -191,7 +186,7 @@ u64 tag_sizeof(tag_t tag)
   {
   case TAG_NIL:
     return 0;
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
     return sizeof(lisp_t *);
   case TAG_CONS:

src/reader.c

@@ -111,7 +111,7 @@ read_err_t read_negative(sys_t *sys, stream_t *stream, lisp_t **ret)
     read_err_t err = read_int(sys, stream, ret);
     if (err)
       return err;
-    i64 n = as_int(*ret);
+    i64 n = as_smi(*ret);
     n *= -1;
     *ret = make_int(n);
     return READ_ERR_OK;

src/sys.c

@@ -46,7 +46,7 @@ void sys_free(sys_t *sys)
 
 lisp_t *make_int(i64 i)
 {
-  return tag_int(i);
+  return tag_smi(i);
 }
 
 lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
@@ -102,7 +102,7 @@ void lisp_free(lisp_t *item)
     break;
   }
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   case NUM_TAGS:
     // shouldn't be dealt with (either constant or dealt with elsewhere)
@@ -134,7 +134,7 @@ void lisp_free_rec(lisp_t *item)
     break;
   }
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   case NUM_TAGS:
     // shouldn't be dealt with (either constant or dealt with elsewhere)

test/test_lisp_api.c

@@ -23,7 +23,7 @@ void smi_test(void)
   {
     i64 in       = ints[i];
     lisp_t *lisp = make_int(in);
-    i64 out      = as_int(lisp);
+    i64 out      = as_smi(lisp);
 
     TEST(in == out, "%ld == %ld", in, out);
   }
@@ -47,7 +47,7 @@ void smi_oob_test(void)
   {
     i64 in       = ints[i];
     lisp_t *lisp = make_int(in);
-    i64 out      = as_int(lisp);
+    i64 out      = as_smi(lisp);
 
     TEST(in != out, "%ld != %ld", in, out);
   }