Improve the experimental local and scoped allocation.

* configure.ac (HAVE_STRUCT_ATTRIBUTE_ALIGNED)
(HAVE_STATEMENT_EXPRESSIONS): New configure-time checks.
* src/alloc.c (local_string_init, local_vector_init):
New functions, defined if USE_LOCAL_ALLOCATORS.
Mostly, these are moved here from lisp.h, as it's not
clear it's worth making them inline.
* src/lisp.h (USE_STACK_LISP_OBJECTS): Default to false.
(GCALIGNED): Depend on HAVE_STRUCT_ATTRIBUTE_ALIGNED and
USE_STACK_LISP_OBJECTS, not on a laundry list.
(local_string_init, local_vector_init): New decls.
(union Aligned_Cons): New type.
(scoped_cons): Use it.  Give up on the char trick, as it's a too
much of a maintenance hassle; if someone wants this speedup
they'll just need to convince their compiler to align properly.
Conversely, use the speedup if struct Lisp_Cons happens to
be aligned even without a directive.  Better yet, help it along
by using union Aligned_Cons rather than struct Lisp_Cons.
(pointer_valid_for_lisp_object): Remove.  This check is not
necessary, since make_lisp_ptr is already doing it.  All uses removed.
(local_vector_init, local_string_init): Move to alloc.c.
(build_local_vector): Remove this awkward macro, replacing with ...
(make_local_vector): New macro, which acts more like a function.
Use statement expressions and use __COUNTER__ to avoid macro
capture.  Fall back on functions if these features are not supported.
(build_local_string, make_local_string): Likewise.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 5c7ce31cad8..714827f6ae3 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2226,6 +2226,32 @@ make_string (const char *contents, ptrdiff_t nbytes)
   return val;
 }
 
+#ifdef USE_LOCAL_ALLOCATORS
+
+/* Initialize the string S from DATA and SIZE.  S must be followed by
+   SIZE + 1 bytes of memory that can be used.  Return S tagged as a
+   Lisp object.  */
+
+Lisp_Object
+local_string_init (struct Lisp_String *s, char const *data, ptrdiff_t size)
+{
+  unsigned char *data_copy = (unsigned char *) (s + 1);
+  parse_str_as_multibyte ((unsigned char const *) data,
+                          size, &s->size, &s->size_byte);
+  if (size == s->size || size != s->size_byte)
+    {
+      s->size = size;
+      s->size_byte = -1;
+    }
+  s->intervals = NULL;
+  s->data = data_copy;
+  memcpy (data_copy, data, size);
+  data_copy[size] = '\0';
+  return make_lisp_ptr (s, Lisp_String);
+}
+
+#endif
+
 
 /* Make an unibyte string from LENGTH bytes at CONTENTS.  */
 
@@ -3288,6 +3314,22 @@ See also the function `vector'.  */)
   return vector;
 }
 
+#ifdef USE_LOCAL_ALLOCATORS
+
+/* Initialize V with LENGTH objects each with value INIT,
+   and return it tagged as a Lisp Object.  */
+
+INLINE Lisp_Object
+local_vector_init (struct Lisp_Vector *v, ptrdiff_t length, Lisp_Object init)
+{
+  v->header.size = length;
+  for (ptrdiff_t i = 0; i < length; i++)
+    v->contents[i] = init;
+  return make_lisp_ptr (v, Lisp_Vectorlike);
+}
+
+#endif
+
 
 DEFUN ("vector", Fvector, Svector, 0, MANY, 0,
        doc: /* Return a newly created vector with specified arguments as elements.