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Re: Inefficiency in Bgotoifnil byte-code instruction


From: Tom Tromey
Subject: Re: Inefficiency in Bgotoifnil byte-code instruction
Date: Mon, 02 Jul 2012 13:17:37 -0600
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux)

Stefan> Could be, yes.  Could you re-post the URL to the latest/cleanest version
Stefan> of it?

I pulled it from the bug:

    http://debbugs.gnu.org/cgi/bugreport.cgi?bug=4470

(btw, gnus-read-ephemeral-emacs-bug-group is awesome) and rebased it.
The appended bootstraps for me.

No ChangeLog, but I can write one if you are still interested in the
patch.

I didn't do any performance testing this time around.


FWIW I suspect a bigger win would be had by applying this treatment --
or even better, a full threaded interpreter -- to the regexp matcher.
Back when I did some profiling of Emacs, the regexp matcher was higher
in my profiles than the bytecode interpreter.

However, this fact doesn't make this patch less desirable.

Tom

diff --git a/src/bytecode.c b/src/bytecode.c
index 08a02ea..0fe4456 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -54,6 +54,13 @@ by Hallvard:
 /* #define BYTE_CODE_SAFE */
 /* #define BYTE_CODE_METER */
 
+/* If BYTE_CODE_THREADED is defined, then the interpreter will be
+   indirect threaded, using GCC's computed goto extension.  This is
+   incompatible with BYTE_CODE_SAFE and BYTE_CODE_METER.  */
+#if defined (__GNUC__) && !defined (BYTE_CODE_SAFE) && !defined 
(BYTE_CODE_METER)
+#define BYTE_CODE_THREADED
+#endif
+
 
 #ifdef BYTE_CODE_METER
 
@@ -84,11 +91,53 @@ Lisp_Object Qbytecode;
 /*  Byte codes: */
 
 #define Bstack_ref 0 /* Actually, Bstack_ref+0 is not implemented: use dup.  */
+#define Bstack_ref1 1
+#define Bstack_ref2 2
+#define Bstack_ref3 3
+#define Bstack_ref4 4
+#define Bstack_ref5 5
+#define Bstack_ref6 6
+#define Bstack_ref7 7
 #define Bvarref 010
+#define Bvarref1 011
+#define Bvarref2 012
+#define Bvarref3 013
+#define Bvarref4 014
+#define Bvarref5 015
+#define Bvarref6 016
+#define Bvarref7 017
 #define Bvarset 020
+#define Bvarset1 021
+#define Bvarset2 022
+#define Bvarset3 023
+#define Bvarset4 024
+#define Bvarset5 025
+#define Bvarset6 026
+#define Bvarset7 027
 #define Bvarbind 030
+#define Bvarbind1 031
+#define Bvarbind2 032
+#define Bvarbind3 033
+#define Bvarbind4 034
+#define Bvarbind5 035
+#define Bvarbind6 036
+#define Bvarbind7 037
 #define Bcall 040
+#define Bcall1 041
+#define Bcall2 042
+#define Bcall3 043
+#define Bcall4 044
+#define Bcall5 045
+#define Bcall6 046
+#define Bcall7 047
 #define Bunbind 050
+#define Bunbind1 051
+#define Bunbind2 052
+#define Bunbind3 053
+#define Bunbind4 054
+#define Bunbind5 055
+#define Bunbind6 056
+#define Bunbind7 057
 
 #define Bnth 070
 #define Bsymbolp 071
@@ -561,27 +610,249 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
       this_op = op = FETCH;
       METER_CODE (prev_op, op);
 #else
+#ifndef BYTE_CODE_THREADED
       op = FETCH;
 #endif
+#endif
+
+      /* The interpreter can be compiled one of two ways: as an
+        ordinary switch-based interpreter, or as a threaded
+        interpreter.  The threaded interpreter relies on GCC's
+        computed goto extension, so it is not available everywhere.
+        Threading provides a performance boost.  These macros are how
+        we allow the code to be compiled both ways.  */
+#ifdef BYTE_CODE_THREADED
+      /* The CASE macro introduces an instruction's body.  It is
+        either a label or a case label.  */
+#define CASE(OP) insn_ ## OP
+      /* NEXT is invoked at the end of an instruction to go to the
+        next instruction.  It is either a computed goto, or a
+        plain break.  */
+#define NEXT goto *(targets[op = FETCH])
+      /* FIRST is like NEXT, but is only used at the start of the
+        interpreter body.  In the switch-based interpreter it is the
+        switch, so the threaded definition must include a semicolon.  */
+#define FIRST NEXT;
+      /* Most cases are labeled with the CASE macro, above.
+        CASE_DEFAULT is one exception; it is used if the interpreter
+        being built requires a default case.  The threaded
+        interpreter does not, because the dispatch table is
+        completely filled.  */
+#define CASE_DEFAULT
+      /* This introduces an instruction that is known to call abort.  */
+#define CASE_ABORT CASE (default)
+#else
+      /* See above for the meaning of the various defines.  */
+#define CASE(OP) case OP
+#define NEXT break
+#define FIRST switch (op)
+#define CASE_DEFAULT case 255: default:
+#define CASE_ABORT case 0
+#endif
+
+#ifdef BYTE_CODE_THREADED
+
+      /* A convenience define that saves us a lot of typing and makes
+        the table clearer.  */
+#define LABEL(OP) [OP] = &&insn_ ## OP
+
+      /* This is the dispatch table for the threaded interpreter.  */
+      static const void *const targets[256] =
+       {
+         [0 ... (Bconstant - 1)] = &&insn_default,
+         [Bconstant ... 255] = &&insn_Bconstant,
+
+         LABEL (Bstack_ref1),
+         LABEL (Bstack_ref2),
+         LABEL (Bstack_ref3),
+         LABEL (Bstack_ref4),
+         LABEL (Bstack_ref5),
+         LABEL (Bstack_ref6),
+         LABEL (Bstack_ref7),
+         LABEL (Bvarref),
+         LABEL (Bvarref1),
+         LABEL (Bvarref2),
+         LABEL (Bvarref3),
+         LABEL (Bvarref4),
+         LABEL (Bvarref5),
+         LABEL (Bvarref6),
+         LABEL (Bvarref7),
+         LABEL (Bvarset),
+         LABEL (Bvarset1),
+         LABEL (Bvarset2),
+         LABEL (Bvarset3),
+         LABEL (Bvarset4),
+         LABEL (Bvarset5),
+         LABEL (Bvarset6),
+         LABEL (Bvarset7),
+         LABEL (Bvarbind),
+         LABEL (Bvarbind1),
+         LABEL (Bvarbind2),
+         LABEL (Bvarbind3),
+         LABEL (Bvarbind4),
+         LABEL (Bvarbind5),
+         LABEL (Bvarbind6),
+         LABEL (Bvarbind7),
+         LABEL (Bcall),
+         LABEL (Bcall1),
+         LABEL (Bcall2),
+         LABEL (Bcall3),
+         LABEL (Bcall4),
+         LABEL (Bcall5),
+         LABEL (Bcall6),
+         LABEL (Bcall7),
+         LABEL (Bunbind),
+         LABEL (Bunbind1),
+         LABEL (Bunbind2),
+         LABEL (Bunbind3),
+         LABEL (Bunbind4),
+         LABEL (Bunbind5),
+         LABEL (Bunbind6),
+         LABEL (Bunbind7),
+         LABEL (Bnth),
+         LABEL (Bsymbolp),
+         LABEL (Bconsp),
+         LABEL (Bstringp),
+         LABEL (Blistp),
+         LABEL (Beq),
+         LABEL (Bmemq),
+         LABEL (Bnot),
+         LABEL (Bcar),
+         LABEL (Bcdr),
+         LABEL (Bcons),
+         LABEL (Blist1),
+         LABEL (Blist2),
+         LABEL (Blist3),
+         LABEL (Blist4),
+         LABEL (Blength),
+         LABEL (Baref),
+         LABEL (Baset),
+         LABEL (Bsymbol_value),
+         LABEL (Bsymbol_function),
+         LABEL (Bset),
+         LABEL (Bfset),
+         LABEL (Bget),
+         LABEL (Bsubstring),
+         LABEL (Bconcat2),
+         LABEL (Bconcat3),
+         LABEL (Bconcat4),
+         LABEL (Bsub1),
+         LABEL (Badd1),
+         LABEL (Beqlsign),
+         LABEL (Bgtr),
+         LABEL (Blss),
+         LABEL (Bleq),
+         LABEL (Bgeq),
+         LABEL (Bdiff),
+         LABEL (Bnegate),
+         LABEL (Bplus),
+         LABEL (Bmax),
+         LABEL (Bmin),
+         LABEL (Bmult),
+         LABEL (Bpoint),
+         LABEL (Bsave_current_buffer),
+         LABEL (Bgoto_char),
+         LABEL (Binsert),
+         LABEL (Bpoint_max),
+         LABEL (Bpoint_min),
+         LABEL (Bchar_after),
+         LABEL (Bfollowing_char),
+         LABEL (Bpreceding_char),
+         LABEL (Bcurrent_column),
+         LABEL (Bindent_to),
+         LABEL (Beolp),
+         LABEL (Beobp),
+         LABEL (Bbolp),
+         LABEL (Bbobp),
+         LABEL (Bcurrent_buffer),
+         LABEL (Bset_buffer),
+         LABEL (Bsave_current_buffer_1),
+         LABEL (Binteractive_p),
+         LABEL (Bforward_char),
+         LABEL (Bforward_word),
+         LABEL (Bskip_chars_forward),
+         LABEL (Bskip_chars_backward),
+         LABEL (Bforward_line),
+         LABEL (Bchar_syntax),
+         LABEL (Bbuffer_substring),
+         LABEL (Bdelete_region),
+         LABEL (Bnarrow_to_region),
+         LABEL (Bwiden),
+         LABEL (Bend_of_line),
+         LABEL (Bconstant2),
+         LABEL (Bgoto),
+         LABEL (Bgotoifnil),
+         LABEL (Bgotoifnonnil),
+         LABEL (Bgotoifnilelsepop),
+         LABEL (Bgotoifnonnilelsepop),
+         LABEL (Breturn),
+         LABEL (Bdiscard),
+         LABEL (Bdup),
+         LABEL (Bsave_excursion),
+         LABEL (Bsave_window_excursion),
+         LABEL (Bsave_restriction),
+         LABEL (Bcatch),
+         LABEL (Bunwind_protect),
+         LABEL (Bcondition_case),
+         LABEL (Btemp_output_buffer_setup),
+         LABEL (Btemp_output_buffer_show),
+         LABEL (Bunbind_all),
+         LABEL (Bset_marker),
+         LABEL (Bmatch_beginning),
+         LABEL (Bmatch_end),
+         LABEL (Bupcase),
+         LABEL (Bdowncase),
+         LABEL (Bstringeqlsign),
+         LABEL (Bstringlss),
+         LABEL (Bequal),
+         LABEL (Bnthcdr),
+         LABEL (Belt),
+         LABEL (Bmember),
+         LABEL (Bassq),
+         LABEL (Bnreverse),
+         LABEL (Bsetcar),
+         LABEL (Bsetcdr),
+         LABEL (Bcar_safe),
+         LABEL (Bcdr_safe),
+         LABEL (Bnconc),
+         LABEL (Bquo),
+         LABEL (Brem),
+         LABEL (Bnumberp),
+         LABEL (Bintegerp),
+         LABEL (BRgoto),
+         LABEL (BRgotoifnil),
+         LABEL (BRgotoifnonnil),
+         LABEL (BRgotoifnilelsepop),
+         LABEL (BRgotoifnonnilelsepop),
+         LABEL (BlistN),
+         LABEL (BconcatN),
+         LABEL (BinsertN),
+         LABEL (Bstack_set),
+         LABEL (Bstack_set2),
+         LABEL (BdiscardN),
+         LABEL (Bconstant)
+       };
+#endif
+
 
-      switch (op)
+      FIRST
        {
-       case Bvarref + 7:
+       CASE (Bvarref7):
          op = FETCH2;
          goto varref;
 
-       case Bvarref:
-       case Bvarref + 1:
-       case Bvarref + 2:
-       case Bvarref + 3:
-       case Bvarref + 4:
-       case Bvarref + 5:
+       CASE (Bvarref):
+       CASE (Bvarref1):
+       CASE (Bvarref2):
+       CASE (Bvarref3):
+       CASE (Bvarref4):
+       CASE (Bvarref5):
          op = op - Bvarref;
          goto varref;
 
        /* This seems to be the most frequently executed byte-code
           among the Bvarref's, so avoid a goto here.  */
-       case Bvarref+6:
+       CASE (Bvarref6):
          op = FETCH;
        varref:
          {
@@ -606,10 +877,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                AFTER_POTENTIAL_GC ();
              }
            PUSH (v2);
-           break;
+           NEXT;
          }
 
-       case Bgotoifnil:
+       CASE (Bgotoifnil):
          {
            Lisp_Object v1;
            MAYBE_GC ();
@@ -621,10 +892,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                CHECK_RANGE (op);
                stack.pc = stack.byte_string_start + op;
              }
-           break;
+           NEXT;
          }
 
-       case Bcar:
+       CASE (Bcar):
          {
            Lisp_Object v1;
            v1 = TOP;
@@ -638,28 +909,28 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                wrong_type_argument (Qlistp, v1);
                AFTER_POTENTIAL_GC ();
              }
-           break;
+           NEXT;
          }
 
-       case Beq:
+       CASE (Beq):
          {
            Lisp_Object v1;
            v1 = POP;
            TOP = EQ (v1, TOP) ? Qt : Qnil;
-           break;
+           NEXT;
          }
 
-       case Bmemq:
+       CASE (Bmemq):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fmemq (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bcdr:
+       CASE (Bcdr):
          {
            Lisp_Object v1;
            v1 = TOP;
@@ -673,24 +944,23 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                wrong_type_argument (Qlistp, v1);
                AFTER_POTENTIAL_GC ();
              }
-           break;
-           break;
+           NEXT;
          }
 
-       case Bvarset:
-       case Bvarset+1:
-       case Bvarset+2:
-       case Bvarset+3:
-       case Bvarset+4:
-       case Bvarset+5:
+       CASE (Bvarset):
+       CASE (Bvarset1):
+       CASE (Bvarset2):
+       CASE (Bvarset3):
+       CASE (Bvarset4):
+       CASE (Bvarset5):
          op -= Bvarset;
          goto varset;
 
-       case Bvarset+7:
+       CASE (Bvarset7):
          op = FETCH2;
          goto varset;
 
-       case Bvarset+6:
+       CASE (Bvarset6):
          op = FETCH;
        varset:
          {
@@ -713,54 +983,54 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
              }
          }
          (void) POP;
-         break;
+         NEXT;
 
-       case Bdup:
+       CASE (Bdup):
          {
            Lisp_Object v1;
            v1 = TOP;
            PUSH (v1);
-           break;
+           NEXT;
          }
 
        /* ------------------ */
 
-       case Bvarbind+6:
+       CASE (Bvarbind6):
          op = FETCH;
          goto varbind;
 
-       case Bvarbind+7:
+       CASE (Bvarbind7):
          op = FETCH2;
          goto varbind;
 
-       case Bvarbind:
-       case Bvarbind+1:
-       case Bvarbind+2:
-       case Bvarbind+3:
-       case Bvarbind+4:
-       case Bvarbind+5:
+       CASE (Bvarbind):
+       CASE (Bvarbind1):
+       CASE (Bvarbind2):
+       CASE (Bvarbind3):
+       CASE (Bvarbind4):
+       CASE (Bvarbind5):
          op -= Bvarbind;
        varbind:
          /* Specbind can signal and thus GC.  */
          BEFORE_POTENTIAL_GC ();
          specbind (vectorp[op], POP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bcall+6:
+       CASE (Bcall6):
          op = FETCH;
          goto docall;
 
-       case Bcall+7:
+       CASE (Bcall7):
          op = FETCH2;
          goto docall;
 
-       case Bcall:
-       case Bcall+1:
-       case Bcall+2:
-       case Bcall+3:
-       case Bcall+4:
-       case Bcall+5:
+       CASE (Bcall):
+       CASE (Bcall1):
+       CASE (Bcall2):
+       CASE (Bcall3):
+       CASE (Bcall4):
+       CASE (Bcall5):
          op -= Bcall;
        docall:
          {
@@ -783,47 +1053,47 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
 #endif
            TOP = Ffuncall (op + 1, &TOP);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bunbind+6:
+       CASE (Bunbind6):
          op = FETCH;
          goto dounbind;
 
-       case Bunbind+7:
+       CASE (Bunbind7):
          op = FETCH2;
          goto dounbind;
 
-       case Bunbind:
-       case Bunbind+1:
-       case Bunbind+2:
-       case Bunbind+3:
-       case Bunbind+4:
-       case Bunbind+5:
+       CASE (Bunbind):
+       CASE (Bunbind1):
+       CASE (Bunbind2):
+       CASE (Bunbind3):
+       CASE (Bunbind4):
+       CASE (Bunbind5):
          op -= Bunbind;
        dounbind:
          BEFORE_POTENTIAL_GC ();
          unbind_to (SPECPDL_INDEX () - op, Qnil);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bunbind_all:       /* Obsolete.  Never used.  */
+       CASE (Bunbind_all):     /* Obsolete.  Never used.  */
          /* To unbind back to the beginning of this frame.  Not used yet,
             but will be needed for tail-recursion elimination.  */
          BEFORE_POTENTIAL_GC ();
          unbind_to (count, Qnil);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bgoto:
+       CASE (Bgoto):
          MAYBE_GC ();
          BYTE_CODE_QUIT;
          op = FETCH2;    /* pc = FETCH2 loses since FETCH2 contains pc++ */
          CHECK_RANGE (op);
          stack.pc = stack.byte_string_start + op;
-         break;
+         NEXT;
 
-       case Bgotoifnonnil:
+       CASE (Bgotoifnonnil):
          {
            Lisp_Object v1;
            MAYBE_GC ();
@@ -835,10 +1105,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                CHECK_RANGE (op);
                stack.pc = stack.byte_string_start + op;
              }
-           break;
+           NEXT;
          }
 
-       case Bgotoifnilelsepop:
+       CASE (Bgotoifnilelsepop):
          MAYBE_GC ();
          op = FETCH2;
          if (NILP (TOP))
@@ -848,9 +1118,9 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
              stack.pc = stack.byte_string_start + op;
            }
          else DISCARD (1);
-         break;
+         NEXT;
 
-       case Bgotoifnonnilelsepop:
+       CASE (Bgotoifnonnilelsepop):
          MAYBE_GC ();
          op = FETCH2;
          if (!NILP (TOP))
@@ -860,15 +1130,15 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
              stack.pc = stack.byte_string_start + op;
            }
          else DISCARD (1);
-         break;
+         NEXT;
 
-       case BRgoto:
+       CASE (BRgoto):
          MAYBE_GC ();
          BYTE_CODE_QUIT;
          stack.pc += (int) *stack.pc - 127;
-         break;
+         NEXT;
 
-       case BRgotoifnil:
+       CASE (BRgotoifnil):
          {
            Lisp_Object v1;
            MAYBE_GC ();
@@ -879,10 +1149,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                stack.pc += (int) *stack.pc - 128;
              }
            stack.pc++;
-           break;
+           NEXT;
          }
 
-       case BRgotoifnonnil:
+       CASE (BRgotoifnonnil):
          {
            Lisp_Object v1;
            MAYBE_GC ();
@@ -893,10 +1163,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
                stack.pc += (int) *stack.pc - 128;
              }
            stack.pc++;
-           break;
+           NEXT;
          }
 
-       case BRgotoifnilelsepop:
+       CASE (BRgotoifnilelsepop):
          MAYBE_GC ();
          op = *stack.pc++;
          if (NILP (TOP))
@@ -905,9 +1175,9 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
              stack.pc += op - 128;
            }
          else DISCARD (1);
-         break;
+         NEXT;
 
-       case BRgotoifnonnilelsepop:
+       CASE (BRgotoifnonnilelsepop):
          MAYBE_GC ();
          op = *stack.pc++;
          if (!NILP (TOP))
@@ -916,31 +1186,31 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
              stack.pc += op - 128;
            }
          else DISCARD (1);
-         break;
+         NEXT;
 
-       case Breturn:
+       CASE (Breturn):
          result = POP;
          goto exit;
 
-       case Bdiscard:
+       CASE (Bdiscard):
          DISCARD (1);
-         break;
+         NEXT;
 
-       case Bconstant2:
+       CASE (Bconstant2):
          PUSH (vectorp[FETCH2]);
-         break;
+         NEXT;
 
-       case Bsave_excursion:
+       CASE (Bsave_excursion):
          record_unwind_protect (save_excursion_restore,
                                 save_excursion_save ());
-         break;
+         NEXT;
 
-       case Bsave_current_buffer: /* Obsolete since ??.  */
-       case Bsave_current_buffer_1:
+       CASE (Bsave_current_buffer): /* Obsolete since ??.  */
+       CASE (Bsave_current_buffer_1):
          record_unwind_protect (set_buffer_if_live, Fcurrent_buffer ());
-         break;
+         NEXT;
 
-       case Bsave_window_excursion: /* Obsolete since 24.1.  */
+       CASE (Bsave_window_excursion): /* Obsolete since 24.1.  */
          {
            register ptrdiff_t count1 = SPECPDL_INDEX ();
            record_unwind_protect (Fset_window_configuration,
@@ -949,29 +1219,29 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
            TOP = Fprogn (TOP);
            unbind_to (count1, TOP);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bsave_restriction:
+       CASE (Bsave_restriction):
          record_unwind_protect (save_restriction_restore,
                                 save_restriction_save ());
-         break;
+         NEXT;
 
-       case Bcatch:            /* FIXME: ill-suited for lexbind.  */
+       CASE (Bcatch):          /* FIXME: ill-suited for lexbind.  */
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = internal_catch (TOP, eval_sub, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bunwind_protect:   /* FIXME: avoid closure for lexbind.  */
+       CASE (Bunwind_protect): /* FIXME: avoid closure for lexbind.  */
          record_unwind_protect (Fprogn, POP);
-         break;
+         NEXT;
 
-       case Bcondition_case:   /* FIXME: ill-suited for lexbind.  */
+       CASE (Bcondition_case): /* FIXME: ill-suited for lexbind.  */
          {
            Lisp_Object handlers, body;
            handlers = POP;
@@ -979,18 +1249,18 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
            BEFORE_POTENTIAL_GC ();
            TOP = internal_lisp_condition_case (TOP, body, handlers);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Btemp_output_buffer_setup: /* Obsolete since 24.1.  */
+       CASE (Btemp_output_buffer_setup): /* Obsolete since 24.1.  */
          BEFORE_POTENTIAL_GC ();
          CHECK_STRING (TOP);
          temp_output_buffer_setup (SSDATA (TOP));
          AFTER_POTENTIAL_GC ();
          TOP = Vstandard_output;
-         break;
+         NEXT;
 
-       case Btemp_output_buffer_show: /* Obsolete since 24.1.  */
+       CASE (Btemp_output_buffer_show): /* Obsolete since 24.1.  */
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
@@ -1000,10 +1270,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
            /* pop binding of standard-output */
            unbind_to (SPECPDL_INDEX () - 1, Qnil);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bnth:
+       CASE (Bnth):
          {
            Lisp_Object v1, v2;
            EMACS_INT n;
@@ -1018,173 +1288,173 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
            immediate_quit = 0;
            TOP = CAR (v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bsymbolp:
+       CASE (Bsymbolp):
          TOP = SYMBOLP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
-       case Bconsp:
+       CASE (Bconsp):
          TOP = CONSP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
-       case Bstringp:
+       CASE (Bstringp):
          TOP = STRINGP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
-       case Blistp:
+       CASE (Blistp):
          TOP = CONSP (TOP) || NILP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
-       case Bnot:
+       CASE (Bnot):
          TOP = NILP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
-       case Bcons:
+       CASE (Bcons):
          {
            Lisp_Object v1;
            v1 = POP;
            TOP = Fcons (TOP, v1);
-           break;
+           NEXT;
          }
 
-       case Blist1:
+       CASE (Blist1):
          TOP = Fcons (TOP, Qnil);
-         break;
+         NEXT;
 
-       case Blist2:
+       CASE (Blist2):
          {
            Lisp_Object v1;
            v1 = POP;
            TOP = Fcons (TOP, Fcons (v1, Qnil));
-           break;
+           NEXT;
          }
 
-       case Blist3:
+       CASE (Blist3):
          DISCARD (2);
          TOP = Flist (3, &TOP);
-         break;
+         NEXT;
 
-       case Blist4:
+       CASE (Blist4):
          DISCARD (3);
          TOP = Flist (4, &TOP);
-         break;
+         NEXT;
 
-       case BlistN:
+       CASE (BlistN):
          op = FETCH;
          DISCARD (op - 1);
          TOP = Flist (op, &TOP);
-         break;
+         NEXT;
 
-       case Blength:
+       CASE (Blength):
          BEFORE_POTENTIAL_GC ();
          TOP = Flength (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Baref:
+       CASE (Baref):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Faref (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Baset:
+       CASE (Baset):
          {
            Lisp_Object v1, v2;
            BEFORE_POTENTIAL_GC ();
            v2 = POP; v1 = POP;
            TOP = Faset (TOP, v1, v2);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bsymbol_value:
+       CASE (Bsymbol_value):
          BEFORE_POTENTIAL_GC ();
          TOP = Fsymbol_value (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bsymbol_function:
+       CASE (Bsymbol_function):
          BEFORE_POTENTIAL_GC ();
          TOP = Fsymbol_function (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bset:
+       CASE (Bset):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fset (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bfset:
+       CASE (Bfset):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Ffset (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bget:
+       CASE (Bget):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fget (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bsubstring:
+       CASE (Bsubstring):
          {
            Lisp_Object v1, v2;
            BEFORE_POTENTIAL_GC ();
            v2 = POP; v1 = POP;
            TOP = Fsubstring (TOP, v1, v2);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bconcat2:
+       CASE (Bconcat2):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fconcat (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bconcat3:
+       CASE (Bconcat3):
          BEFORE_POTENTIAL_GC ();
          DISCARD (2);
          TOP = Fconcat (3, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bconcat4:
+       CASE (Bconcat4):
          BEFORE_POTENTIAL_GC ();
          DISCARD (3);
          TOP = Fconcat (4, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case BconcatN:
+       CASE (BconcatN):
          op = FETCH;
          BEFORE_POTENTIAL_GC ();
          DISCARD (op - 1);
          TOP = Fconcat (op, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bsub1:
+       CASE (Bsub1):
          {
            Lisp_Object v1;
            v1 = TOP;
@@ -1199,10 +1469,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
                TOP = Fsub1 (v1);
                AFTER_POTENTIAL_GC ();
              }
-           break;
+           NEXT;
          }
 
-       case Badd1:
+       CASE (Badd1):
          {
            Lisp_Object v1;
            v1 = TOP;
@@ -1217,10 +1487,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
                TOP = Fadd1 (v1);
                AFTER_POTENTIAL_GC ();
              }
-           break;
+           NEXT;
          }
 
-       case Beqlsign:
+       CASE (Beqlsign):
          {
            Lisp_Object v1, v2;
            BEFORE_POTENTIAL_GC ();
@@ -1238,57 +1508,57 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
              }
            else
              TOP = (XINT (v1) == XINT (v2) ? Qt : Qnil);
-           break;
+           NEXT;
          }
 
-       case Bgtr:
+       CASE (Bgtr):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fgtr (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Blss:
+       CASE (Blss):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Flss (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bleq:
+       CASE (Bleq):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fleq (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bgeq:
+       CASE (Bgeq):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fgeq (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bdiff:
+       CASE (Bdiff):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fminus (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bnegate:
+       CASE (Bnegate):
          {
            Lisp_Object v1;
            v1 = TOP;
@@ -1303,209 +1573,209 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
                TOP = Fminus (1, &TOP);
                AFTER_POTENTIAL_GC ();
              }
-           break;
+           NEXT;
          }
 
-       case Bplus:
+       CASE (Bplus):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fplus (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bmax:
+       CASE (Bmax):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fmax (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bmin:
+       CASE (Bmin):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fmin (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bmult:
+       CASE (Bmult):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Ftimes (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bquo:
+       CASE (Bquo):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fquo (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Brem:
+       CASE (Brem):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Frem (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bpoint:
+       CASE (Bpoint):
          {
            Lisp_Object v1;
            XSETFASTINT (v1, PT);
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bgoto_char:
+       CASE (Bgoto_char):
          BEFORE_POTENTIAL_GC ();
          TOP = Fgoto_char (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Binsert:
+       CASE (Binsert):
          BEFORE_POTENTIAL_GC ();
          TOP = Finsert (1, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case BinsertN:
+       CASE (BinsertN):
          op = FETCH;
          BEFORE_POTENTIAL_GC ();
          DISCARD (op - 1);
          TOP = Finsert (op, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bpoint_max:
+       CASE (Bpoint_max):
          {
            Lisp_Object v1;
            XSETFASTINT (v1, ZV);
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bpoint_min:
+       CASE (Bpoint_min):
          {
            Lisp_Object v1;
            XSETFASTINT (v1, BEGV);
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bchar_after:
+       CASE (Bchar_after):
          BEFORE_POTENTIAL_GC ();
          TOP = Fchar_after (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bfollowing_char:
+       CASE (Bfollowing_char):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = Ffollowing_char ();
            AFTER_POTENTIAL_GC ();
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bpreceding_char:
+       CASE (Bpreceding_char):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = Fprevious_char ();
            AFTER_POTENTIAL_GC ();
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bcurrent_column:
+       CASE (Bcurrent_column):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            XSETFASTINT (v1, current_column ());
            AFTER_POTENTIAL_GC ();
            PUSH (v1);
-           break;
+           NEXT;
          }
 
-       case Bindent_to:
+       CASE (Bindent_to):
          BEFORE_POTENTIAL_GC ();
          TOP = Findent_to (TOP, Qnil);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Beolp:
+       CASE (Beolp):
          PUSH (Feolp ());
-         break;
+         NEXT;
 
-       case Beobp:
+       CASE (Beobp):
          PUSH (Feobp ());
-         break;
+         NEXT;
 
-       case Bbolp:
+       CASE (Bbolp):
          PUSH (Fbolp ());
-         break;
+         NEXT;
 
-       case Bbobp:
+       CASE (Bbobp):
          PUSH (Fbobp ());
-         break;
+         NEXT;
 
-       case Bcurrent_buffer:
+       CASE (Bcurrent_buffer):
          PUSH (Fcurrent_buffer ());
-         break;
+         NEXT;
 
-       case Bset_buffer:
+       CASE (Bset_buffer):
          BEFORE_POTENTIAL_GC ();
          TOP = Fset_buffer (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Binteractive_p:    /* Obsolete since 24.1.  */
+       CASE (Binteractive_p):  /* Obsolete since 24.1.  */
          PUSH (Finteractive_p ());
-         break;
+         NEXT;
 
-       case Bforward_char:
+       CASE (Bforward_char):
          BEFORE_POTENTIAL_GC ();
          TOP = Fforward_char (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bforward_word:
+       CASE (Bforward_word):
          BEFORE_POTENTIAL_GC ();
          TOP = Fforward_word (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bskip_chars_forward:
+       CASE (Bskip_chars_forward):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fskip_chars_forward (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bskip_chars_backward:
+       CASE (Bskip_chars_backward):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fskip_chars_backward (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bforward_line:
+       CASE (Bforward_line):
          BEFORE_POTENTIAL_GC ();
          TOP = Fforward_line (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bchar_syntax:
+       CASE (Bchar_syntax):
          {
            int c;
 
@@ -1517,51 +1787,51 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
              MAKE_CHAR_MULTIBYTE (c);
            XSETFASTINT (TOP, syntax_code_spec[(int) SYNTAX (c)]);
          }
-         break;
+         NEXT;
 
-       case Bbuffer_substring:
+       CASE (Bbuffer_substring):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fbuffer_substring (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bdelete_region:
+       CASE (Bdelete_region):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fdelete_region (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bnarrow_to_region:
+       CASE (Bnarrow_to_region):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fnarrow_to_region (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bwiden:
+       CASE (Bwiden):
          BEFORE_POTENTIAL_GC ();
          PUSH (Fwiden ());
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bend_of_line:
+       CASE (Bend_of_line):
          BEFORE_POTENTIAL_GC ();
          TOP = Fend_of_line (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bset_marker:
+       CASE (Bset_marker):
          {
            Lisp_Object v1, v2;
            BEFORE_POTENTIAL_GC ();
@@ -1569,72 +1839,72 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
            v2 = POP;
            TOP = Fset_marker (TOP, v2, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bmatch_beginning:
+       CASE (Bmatch_beginning):
          BEFORE_POTENTIAL_GC ();
          TOP = Fmatch_beginning (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bmatch_end:
+       CASE (Bmatch_end):
          BEFORE_POTENTIAL_GC ();
          TOP = Fmatch_end (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bupcase:
+       CASE (Bupcase):
          BEFORE_POTENTIAL_GC ();
          TOP = Fupcase (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bdowncase:
+       CASE (Bdowncase):
          BEFORE_POTENTIAL_GC ();
          TOP = Fdowncase (TOP);
          AFTER_POTENTIAL_GC ();
-       break;
+       NEXT;
 
-       case Bstringeqlsign:
+      CASE (Bstringeqlsign):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fstring_equal (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bstringlss:
+       CASE (Bstringlss):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fstring_lessp (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bequal:
+       CASE (Bequal):
          {
            Lisp_Object v1;
            v1 = POP;
            TOP = Fequal (TOP, v1);
-           break;
+           NEXT;
          }
 
-       case Bnthcdr:
+       CASE (Bnthcdr):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fnthcdr (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Belt:
+       CASE (Belt):
          {
            Lisp_Object v1, v2;
            if (CONSP (TOP))
@@ -1660,87 +1930,91 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
                TOP = Felt (TOP, v1);
                AFTER_POTENTIAL_GC ();
              }
-           break;
+           NEXT;
          }
 
-       case Bmember:
+       CASE (Bmember):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fmember (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bassq:
+       CASE (Bassq):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fassq (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bnreverse:
+       CASE (Bnreverse):
          BEFORE_POTENTIAL_GC ();
          TOP = Fnreverse (TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bsetcar:
+       CASE (Bsetcar):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fsetcar (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bsetcdr:
+       CASE (Bsetcdr):
          {
            Lisp_Object v1;
            BEFORE_POTENTIAL_GC ();
            v1 = POP;
            TOP = Fsetcdr (TOP, v1);
            AFTER_POTENTIAL_GC ();
-           break;
+           NEXT;
          }
 
-       case Bcar_safe:
+       CASE (Bcar_safe):
          {
            Lisp_Object v1;
            v1 = TOP;
            TOP = CAR_SAFE (v1);
-           break;
+           NEXT;
          }
 
-       case Bcdr_safe:
+       CASE (Bcdr_safe):
          {
            Lisp_Object v1;
            v1 = TOP;
            TOP = CDR_SAFE (v1);
-           break;
+           NEXT;
          }
 
-       case Bnconc:
+       CASE (Bnconc):
          BEFORE_POTENTIAL_GC ();
          DISCARD (1);
          TOP = Fnconc (2, &TOP);
          AFTER_POTENTIAL_GC ();
-         break;
+         NEXT;
 
-       case Bnumberp:
+       CASE (Bnumberp):
          TOP = (NUMBERP (TOP) ? Qt : Qnil);
-         break;
+         NEXT;
 
-       case Bintegerp:
+       CASE (Bintegerp):
          TOP = INTEGERP (TOP) ? Qt : Qnil;
-         break;
+         NEXT;
 
 #ifdef BYTE_CODE_SAFE
+         /* These are intentionally written using 'case' syntax,
+            because they are incompatible with the threaded
+            interpreter.  */
+
        case Bset_mark:
          BEFORE_POTENTIAL_GC ();
          error ("set-mark is an obsolete bytecode");
@@ -1753,49 +2027,49 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
          break;
 #endif
 
-       case 0:
+       CASE_ABORT:
          /* Actually this is Bstack_ref with offset 0, but we use Bdup
             for that instead.  */
-         /* case Bstack_ref: */
+         /* CASE (Bstack_ref): */
          abort ();
 
          /* Handy byte-codes for lexical binding.  */
-       case Bstack_ref+1:
-       case Bstack_ref+2:
-       case Bstack_ref+3:
-       case Bstack_ref+4:
-       case Bstack_ref+5:
+       CASE (Bstack_ref1):
+       CASE (Bstack_ref2):
+       CASE (Bstack_ref3):
+       CASE (Bstack_ref4):
+       CASE (Bstack_ref5):
          {
            Lisp_Object *ptr = top - (op - Bstack_ref);
            PUSH (*ptr);
-           break;
+           NEXT;
          }
-       case Bstack_ref+6:
+       CASE (Bstack_ref6):
          {
            Lisp_Object *ptr = top - (FETCH);
            PUSH (*ptr);
-           break;
+           NEXT;
          }
-       case Bstack_ref+7:
+       CASE (Bstack_ref7):
          {
            Lisp_Object *ptr = top - (FETCH2);
            PUSH (*ptr);
-           break;
+           NEXT;
          }
-       case Bstack_set:
+       CASE (Bstack_set):
          /* stack-set-0 = discard; stack-set-1 = discard-1-preserve-tos.  */
          {
            Lisp_Object *ptr = top - (FETCH);
            *ptr = POP;
-           break;
+           NEXT;
          }
-       case Bstack_set2:
+       CASE (Bstack_set2):
          {
            Lisp_Object *ptr = top - (FETCH2);
            *ptr = POP;
-           break;
+           NEXT;
          }
-       case BdiscardN:
+       CASE (BdiscardN):
          op = FETCH;
          if (op & 0x80)
            {
@@ -1803,10 +2077,10 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object 
vector, Lisp_Object maxdepth,
              top[-op] = TOP;
            }
          DISCARD (op);
-         break;
+         NEXT;
 
-       case 255:
-       default:
+       CASE_DEFAULT
+       CASE (Bconstant):
 #ifdef BYTE_CODE_SAFE
          if (op < Bconstant)
            {
@@ -1820,6 +2094,7 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, 
Lisp_Object maxdepth,
 #else
          PUSH (vectorp[op - Bconstant]);
 #endif
+         NEXT;
        }
     }
 



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