Use float instead of Lisp_Object for rehash_size

* src/alloc.c (purecopy_hash_table):
* src/fns.c (maybe_resize_hash_table, Fmake_hash_table):
(Fhash_table_rehash_size):
* src/lisp.h (struct Lisp_Hash_Table.rehash_size):
The rehash_size member of struct Lisp_Hash_Table is now a
float, not a Lisp_Object.
* src/alloc.c (purecopy_hash_table): Assign members in order.
* src/fns.c (make_hash_table): Use EMACS_INT for size and
float for rehash_size, instead of Lisp_Object for both.
All callers changed.
* src/lisp.h (DEFAULT_REHASH_SIZE): Now float, not double,
and 1 smaller.
* src/print.c (print_object): Simplify by calling
Fhash_table_rehash_size and Fhash_table_rehash_threshold.
Avoid unnecessary NILP.

9 files changed, 81 insertions, 76 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 5da4290701e..b44b90e558a 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -5453,18 +5453,18 @@ purecopy_hash_table (struct Lisp_Hash_Table *table)
   pure_test.user_hash_function = purecopy (table->test.user_hash_function);
   pure_test.user_cmp_function = purecopy (table->test.user_cmp_function);
 
-  pure->test = pure_test;
   pure->header = table->header;
   pure->weak = purecopy (Qnil);
-  pure->rehash_size = purecopy (table->rehash_size);
   pure->hash = purecopy (table->hash);
   pure->next = purecopy (table->next);
-  pure->next_free = table->next_free;
   pure->index = purecopy (table->index);
   pure->count = table->count;
+  pure->next_free = table->next_free;
   pure->pure = table->pure;
   pure->rehash_threshold = table->rehash_threshold;
+  pure->rehash_size = table->rehash_size;
   pure->key_and_value = purecopy (table->key_and_value);
+  pure->test = pure_test;
 
   return pure;
 }
diff --git a/src/category.c b/src/category.c
index f5edd20c8a3..b633f65532a 100644
--- a/src/category.c
+++ b/src/category.c
@@ -64,9 +64,8 @@ hash_get_category_set (Lisp_Object table, Lisp_Object category_set)
   if (NILP (XCHAR_TABLE (table)->extras[1]))
     set_char_table_extras
       (table, 1,
-       make_hash_table (hashtest_equal, make_number (DEFAULT_HASH_SIZE),
-                        make_float (DEFAULT_REHASH_SIZE),
-                        DEFAULT_REHASH_THRESHOLD,
+       make_hash_table (hashtest_equal, DEFAULT_HASH_SIZE,
+                        DEFAULT_REHASH_SIZE, DEFAULT_REHASH_THRESHOLD,
                         Qnil, false));
   h = XHASH_TABLE (XCHAR_TABLE (table)->extras[1]);
   i = hash_lookup (h, category_set, &hash);
diff --git a/src/emacs-module.c b/src/emacs-module.c
index 5a66b516513..1b445dcc3b2 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -1013,9 +1013,8 @@ syms_of_module (void)
                doc: /* Module global reference table.  */);
 
   Vmodule_refs_hash
-    = make_hash_table (hashtest_eq, make_number (DEFAULT_HASH_SIZE),
-                       make_float (DEFAULT_REHASH_SIZE),
-                       DEFAULT_REHASH_THRESHOLD,
+    = make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE,
+                       DEFAULT_REHASH_SIZE, DEFAULT_REHASH_THRESHOLD,
                        Qnil, false);
   Funintern (Qmodule_refs_hash, Qnil);
 
diff --git a/src/fns.c b/src/fns.c
index 3769c4efb70..9668c885ab6 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -3684,13 +3684,13 @@ allocate_hash_table (void)
    `equal' or a symbol denoting a user-defined test named TEST with
    test and hash functions USER_TEST and USER_HASH.
 
-   Give the table initial capacity SIZE, SIZE >= 0, an integer.
+   Give the table initial capacity SIZE, 0 <= SIZE <= MOST_POSITIVE_FIXNUM.
 
-   If REHASH_SIZE is an integer, it must be > 0, and this hash table's
-   new size when it becomes full is computed by adding REHASH_SIZE to
-   its old size.  If REHASH_SIZE is a float, it must be > 1.0, and the
-   table's new size is computed by multiplying its old size with
-   REHASH_SIZE.
+   If REHASH_SIZE is equal to a negative integer, this hash table's
+   new size when it becomes full is computed by subtracting
+   REHASH_SIZE from its old size.  Otherwise it must be positive, and
+   the table's new size is computed by multiplying its old size by
+   REHASH_SIZE + 1.
 
    REHASH_THRESHOLD must be a float <= 1.0, and > 0.  The table will
    be resized when the approximate ratio of table entries to table
@@ -3704,34 +3704,31 @@ allocate_hash_table (void)
    changed after purecopy.  */
 
 Lisp_Object
-make_hash_table (struct hash_table_test test,
-                 Lisp_Object size, Lisp_Object rehash_size,
-                 float rehash_threshold, Lisp_Object weak,
-                 bool pure)
+make_hash_table (struct hash_table_test test, EMACS_INT size,
+                 float rehash_size, float rehash_threshold,
+                 Lisp_Object weak, bool pure)
 {
   struct Lisp_Hash_Table *h;
   Lisp_Object table;
-  EMACS_INT index_size, sz;
+  EMACS_INT index_size;
   ptrdiff_t i;
   double index_float;
 
   /* Preconditions.  */
   eassert (SYMBOLP (test.name));
-  eassert (INTEGERP (size) && XINT (size) >= 0);
-  eassert ((INTEGERP (rehash_size) && XINT (rehash_size) > 0)
-           || (FLOATP (rehash_size) && 1 < XFLOAT_DATA (rehash_size)));
+  eassert (0 <= size && size <= MOST_POSITIVE_FIXNUM);
+  eassert (rehash_size <= -1 || 0 < rehash_size);
   eassert (0 < rehash_threshold && rehash_threshold <= 1);
 
-  if (XFASTINT (size) == 0)
-    size = make_number (1);
+  if (size == 0)
+    size = 1;
 
-  sz = XFASTINT (size);
   double threshold = rehash_threshold;
-  index_float = sz / threshold;
+  index_float = size / threshold;
   index_size = (index_float < INDEX_SIZE_BOUND + 1
                 ? next_almost_prime (index_float)
                 : INDEX_SIZE_BOUND + 1);
-  if (INDEX_SIZE_BOUND < max (index_size, 2 * sz))
+  if (INDEX_SIZE_BOUND < max (index_size, 2 * size))
     error ("Hash table too large");
 
   /* Allocate a table and initialize it.  */
@@ -3743,14 +3740,14 @@ make_hash_table (struct hash_table_test test,
   h->rehash_threshold = rehash_threshold;
   h->rehash_size = rehash_size;
   h->count = 0;
-  h->key_and_value = Fmake_vector (make_number (2 * sz), Qnil);
-  h->hash = Fmake_vector (size, Qnil);
-  h->next = Fmake_vector (size, make_number (-1));
+  h->key_and_value = Fmake_vector (make_number (2 * size), Qnil);
+  h->hash = Fmake_vector (make_number (size), Qnil);
+  h->next = Fmake_vector (make_number (size), make_number (-1));
   h->index = Fmake_vector (make_number (index_size), make_number (-1));
   h->pure = pure;
 
   /* Set up the free list.  */
-  for (i = 0; i < sz - 1; ++i)
+  for (i = 0; i < size - 1; ++i)
     set_hash_next_slot (h, i, i + 1);
   h->next_free = 0;
 
@@ -3810,22 +3807,21 @@ maybe_resize_hash_table (struct Lisp_Hash_Table *h)
       ptrdiff_t old_size = HASH_TABLE_SIZE (h);
       EMACS_INT new_size, index_size, nsize;
       ptrdiff_t i;
+      double rehash_size = h->rehash_size;
       double index_float;
 
-      if (INTEGERP (h->rehash_size))
-        new_size = old_size + XFASTINT (h->rehash_size);
+      if (rehash_size < 0)
+        new_size = old_size - rehash_size;
       else
         {
-          double float_new_size = old_size * XFLOAT_DATA (h->rehash_size);
+          double float_new_size = old_size * (rehash_size + 1);
           if (float_new_size < INDEX_SIZE_BOUND + 1)
-            {
-              new_size = float_new_size;
-              if (new_size <= old_size)
-                new_size = old_size + 1;
-            }
+            new_size = float_new_size;
           else
             new_size = INDEX_SIZE_BOUND + 1;
         }
+      if (new_size <= old_size)
+        new_size = old_size + 1;
       double threshold = h->rehash_threshold;
       index_float = new_size / threshold;
       index_size = (index_float < INDEX_SIZE_BOUND + 1
@@ -4408,7 +4404,7 @@ in an error.
 usage: (make-hash-table &rest KEYWORD-ARGS)  */)
   (ptrdiff_t nargs, Lisp_Object *args)
 {
-  Lisp_Object test, size, rehash_size, weak;
+  Lisp_Object test, weak;
   bool pure;
   struct hash_table_test testdesc;
   ptrdiff_t i;
@@ -4448,18 +4444,26 @@ usage: (make-hash-table &rest KEYWORD-ARGS)  */)
   pure = i && !NILP (args[i]);
   /* See if there's a `:size SIZE' argument.  */
   i = get_key_arg (QCsize, nargs, args, used);
-  size = i ? args[i] : Qnil;
-  if (NILP (size))
-    size = make_number (DEFAULT_HASH_SIZE);
-  else if (!INTEGERP (size) || XINT (size) < 0)
-    signal_error ("Invalid hash table size", size);
+  Lisp_Object size_arg = i ? args[i] : Qnil;
+  EMACS_INT size;
+  if (NILP (size_arg))
+    size = DEFAULT_HASH_SIZE;
+  else if (NATNUMP (size_arg))
+    size = XFASTINT (size_arg);
+  else
+    signal_error ("Invalid hash table size", size_arg);
 
   /* Look for `:rehash-size SIZE'.  */
+  float rehash_size;
   i = get_key_arg (QCrehash_size, nargs, args, used);
-  rehash_size = i ? args[i] : make_float (DEFAULT_REHASH_SIZE);
-  if (! ((INTEGERP (rehash_size) && 0 < XINT (rehash_size))
-         || (FLOATP (rehash_size) && 1 < XFLOAT_DATA (rehash_size))))
-    signal_error ("Invalid hash table rehash size", rehash_size);
+  if (!i)
+    rehash_size = DEFAULT_REHASH_SIZE;
+  else if (INTEGERP (args[i]) && 0 < XINT (args[i]))
+    rehash_size = - XINT (args[i]);
+  else if (FLOATP (args[i]) && 0 < (float) (XFLOAT_DATA (args[i]) - 1))
+    rehash_size = (float) (XFLOAT_DATA (args[i]) - 1);
+  else
+    signal_error ("Invalid hash table rehash size", args[i]);
 
   /* Look for `:rehash-threshold THRESHOLD'.  */
   i = get_key_arg (QCrehash_threshold, nargs, args, used);
@@ -4513,7 +4517,14 @@ DEFUN ("hash-table-rehash-size", Fhash_table_rehash_size,
        doc: /* Return the current rehash size of TABLE.  */)
   (Lisp_Object table)
 {
-  return check_hash_table (table)->rehash_size;
+  double rehash_size = check_hash_table (table)->rehash_size;
+  if (rehash_size < 0)
+    {
+      EMACS_INT s = -rehash_size;
+      return make_number (min (s, MOST_POSITIVE_FIXNUM));
+    }
+  else
+    return make_float (rehash_size + 1);
 }
 
 
diff --git a/src/image.c b/src/image.c
index 0a6bbd17d88..fc396c7353d 100644
--- a/src/image.c
+++ b/src/image.c
@@ -4017,9 +4017,8 @@ xpm_make_color_table_h (void (**put_func) (Lisp_Object, const char *, int,
 {
   *put_func = xpm_put_color_table_h;
   *get_func = xpm_get_color_table_h;
-  return make_hash_table (hashtest_equal, make_number (DEFAULT_HASH_SIZE),
-                          make_float (DEFAULT_REHASH_SIZE),
-                          DEFAULT_REHASH_THRESHOLD,
+  return make_hash_table (hashtest_equal, DEFAULT_HASH_SIZE,
+                          DEFAULT_REHASH_SIZE, DEFAULT_REHASH_THRESHOLD,
                           Qnil, false);
 }
 
diff --git a/src/lisp.h b/src/lisp.h
index 027fd07d720..e048011a860 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1969,11 +1969,6 @@ struct Lisp_Hash_Table
      weakness of the table.  */
   Lisp_Object weak;
 
-  /* When the table is resized, and this is an integer, compute the
-     new size by adding this to the old size.  If a float, compute the
-     new size by multiplying the old size with this factor.  */
-  Lisp_Object rehash_size;
-
   /* Vector of hash codes.  If hash[I] is nil, this means that the
      I-th entry is unused.  */
   Lisp_Object hash;
@@ -2008,6 +2003,13 @@ struct Lisp_Hash_Table
      ratio.  */
   float rehash_threshold;
 
+  /* Used when the table is resized.  If equal to a negative integer,
+     the user rehash-size is the integer -REHASH_SIZE, and the new
+     size is the old size plus -REHASH_SIZE.  If positive, the user
+     rehash-size is the floating-point value REHASH_SIZE + 1, and the
+     new size is the old size times REHASH_SIZE + 1.  */
+  float rehash_size;
+
   /* Vector of keys and values.  The key of item I is found at index
      2 * I, the value is found at index 2 * I + 1.
      This is gc_marked specially if the table is weak.  */
@@ -2076,9 +2078,9 @@ enum DEFAULT_HASH_SIZE { DEFAULT_HASH_SIZE = 65 };
 
 static float const DEFAULT_REHASH_THRESHOLD = 0.8125;
 
-/* Default factor by which to increase the size of a hash table.  */
+/* Default factor by which to increase the size of a hash table, minus 1.  */
 
-static double const DEFAULT_REHASH_SIZE = 1.5;
+static float const DEFAULT_REHASH_SIZE = 1.5 - 1;
 
 /* Combine two integers X and Y for hashing.  The result might not fit
    into a Lisp integer.  */
@@ -3347,10 +3349,8 @@ extern Lisp_Object larger_vector (Lisp_Object, ptrdiff_t, ptrdiff_t);
 extern void sweep_weak_hash_tables (void);
 EMACS_UINT hash_string (char const *, ptrdiff_t);
 EMACS_UINT sxhash (Lisp_Object, int);
-Lisp_Object make_hash_table (struct hash_table_test test,
-                             Lisp_Object size, Lisp_Object rehash_size,
-                             float rehash_threshold, Lisp_Object weak,
-                             bool pure);
+Lisp_Object make_hash_table (struct hash_table_test, EMACS_INT, float, float,
+                             Lisp_Object, bool);
 ptrdiff_t hash_lookup (struct Lisp_Hash_Table *, Lisp_Object, EMACS_UINT *);
 ptrdiff_t hash_put (struct Lisp_Hash_Table *, Lisp_Object, Lisp_Object,
                     EMACS_UINT);
diff --git a/src/print.c b/src/print.c
index 3a36a4eb54d..8c4bb24555e 100644
--- a/src/print.c
+++ b/src/print.c
@@ -1806,14 +1806,12 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
               print_object (h->weak, printcharfun, escapeflag);
             }
 
-          if (!NILP (h->rehash_size))
-            {
-              print_c_string (" rehash-size ", printcharfun);
-              print_object (h->rehash_size, printcharfun, escapeflag);
-            }
+          print_c_string (" rehash-size ", printcharfun);
+          print_object (Fhash_table_rehash_size (obj),
+                        printcharfun, escapeflag);
 
           print_c_string (" rehash-threshold ", printcharfun);
-          print_object (make_float (h->rehash_threshold),
+          print_object (Fhash_table_rehash_threshold (obj),
                         printcharfun, escapeflag);
 
           if (h->pure)
diff --git a/src/profiler.c b/src/profiler.c
index 08ef6ee9623..6dc0d8ce72d 100644
--- a/src/profiler.c
+++ b/src/profiler.c
@@ -44,9 +44,8 @@ make_log (EMACS_INT heap_size, EMACS_INT max_stack_depth)
      a special way.  This is OK as long as the object is not exposed
      to Elisp, i.e. until it is returned by *-profiler-log, after which
      it can't be used any more.  */
-  Lisp_Object log = make_hash_table (hashtest_profiler,
-                                     make_number (heap_size),
-                                     make_float (DEFAULT_REHASH_SIZE),
+  Lisp_Object log = make_hash_table (hashtest_profiler, heap_size,
+                                     DEFAULT_REHASH_SIZE,
                                      DEFAULT_REHASH_THRESHOLD,
                                      Qnil, false);
   struct Lisp_Hash_Table *h = XHASH_TABLE (log);
diff --git a/src/xterm.c b/src/xterm.c
index b04c6999b39..52bc8f9eca2 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -12874,8 +12874,8 @@ keysyms.  The default is nil, which is the same as `super'.  */);
 
   DEFVAR_LISP ("x-keysym-table", Vx_keysym_table,
     doc: /* Hash table of character codes indexed by X keysym codes.  */);
-  Vx_keysym_table = make_hash_table (hashtest_eql, make_number (900),
-                                     make_float (DEFAULT_REHASH_SIZE),
+  Vx_keysym_table = make_hash_table (hashtest_eql, 900,
+                                     DEFAULT_REHASH_SIZE,
                                      DEFAULT_REHASH_THRESHOLD,
                                      Qnil, false);