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, 3 deletions

diff --git a/src/eval.c b/src/eval.c
index 7b7bdd8df7b..f681ef7c278 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -222,7 +222,6 @@ static struct handler handlerlist_sentinel;
 void
 init_eval (void)
 {
-  byte_stack_list = 0;
   specpdl_ptr = specpdl;
   { /* Put a dummy catcher at top-level so that handlerlist is never NULL.
        This is important since handlerlist->nextfree holds the freelist
@@ -1135,7 +1134,6 @@ unwind_to_catch (struct handler *catch, Lisp_Object value)
 
   eassert (handlerlist == catch);
 
-  byte_stack_list = catch->byte_stack;
   lisp_eval_depth = catch->lisp_eval_depth;
 
   sys_longjmp (catch->jmp, 1);
@@ -1430,7 +1428,6 @@ push_handler_nosignal (Lisp_Object tag_ch_val, enum handlertype handlertype)
   c->pdlcount = SPECPDL_INDEX ();
   c->poll_suppress_count = poll_suppress_count;
   c->interrupt_input_blocked = interrupt_input_blocked;
-  c->byte_stack = byte_stack_list;
   handlerlist = c;
   return c;
 }