Remove interpreter’s byte stack

This improves performance overall on my benchmark on x86-64,
since the interpreted program-counter resides in a machine
register rather than in RAM.
* etc/DEBUG, src/.gdbinit: Remove xbytecode GDB command, as there
is no longer a byte stack to decode.
* src/bytecode.c (struct byte_stack, byte_stack_list)
(relocate_byte_stack): Remove.  All uses removed.
(FETCH): Simplify now that pc is now local (typically, in a
register) and no longer needs to be relocated.
(CHECK_RANGE): Remove.  All uses now done inline, in a different way.
(BYTE_CODE_QUIT): Remove; now done by op_relative_branch.
(exec_byte_code): Allocate a copy of the function’s bytecode,
so that there is no problem if GC moves it.
* src/lisp.h (struct handler): Remove byte_stack member.
All uses removed.
(SAFE_ALLOCA_LISP_EXTRA): New macro, a generalization of
SAFE_ALLOCA_LISP.
(SAFE_ALLOCA_LISP): Use it.

1 files changed, 0 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index e25d91ff8aa..db165757e19 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -5799,8 +5799,6 @@ garbage_collect_1 (void *end)
 
   gc_sweep ();
 
-  relocate_byte_stack ();
-
   /* Clear the mark bits that we set in certain root slots.  */
   VECTOR_UNMARK (&buffer_defaults);
   VECTOR_UNMARK (&buffer_local_symbols);