Replace Vdead with tagged pointer

This speeds up ‘make compile-always’ by 0.1% on my platform.
Suggested by Pip Cet in:
https://lists.gnu.org/r/emacs-devel/2019-07/msg00257.html
* src/.gdbinit (pwinx, pgx, xbuffer, xprintstr):
Output dead_object () as "DEAD".
* src/alloc.c (Vdead, DEADP): Remove.
All uses replaced by dead_object () / deadp.
(deadp): New function.
(init_alloc_once_for_pdumper): Remove no-longer-needed
initialization.
* src/lisp.h (dead_object): New function.

1 files changed, 1 insertions, 4 deletions

diff --git a/src/pdumper.c b/src/pdumper.c
index 3d8531c6a43..b80757c2071 100644
--- a/src/pdumper.c
+++ b/src/pdumper.c
@@ -3061,10 +3061,7 @@ dump_object (struct dump_context *ctx, Lisp_Object object)
 #if CHECK_STRUCTS && !defined (HASH_Lisp_Type_E2AD97D3F7)
 # error "Lisp_Type changed. See CHECK_STRUCTS comment in config.h."
 #endif
-#ifdef ENABLE_CHECKING
-  /* Vdead is extern only when ENABLE_CHECKING.  */
-  eassert (!EQ (object, Vdead));
-#endif
+  eassert (!EQ (object, dead_object ()));
 
   dump_off offset = dump_recall_object (ctx, object);
   if (offset > 0)