Get rid of dead code that was introduced for an hypothetical JIT (#9710)

That code was never used and some of it is outdated.

Changes

@@ -77,6 +77,10 @@ Working version
   areas in the page table, subsumed by the new code fragment management API
   (Xavier Leroy, review by Jacques-Henri Jourdan)
 
+- #9710: Drop "support" for an hypothetical JIT for OCaml bytecode
+   which has never existed.
+  (Jacques-Henri Jourdan, review by Xavier Leroy)
+
 ### Code generation and optimizations:
 
 - #9620: Limit the number of parameters for an uncurried or untupled

runtime/callback.c

@@ -36,7 +36,6 @@
 
 CAMLexport int caml_callback_depth = 0;
 
-#ifndef LOCAL_CALLBACK_BYTECODE
 static opcode_t callback_code[] = { ACC, 0, APPLY, 0, POP, 1, STOP };
 
 static int callback_code_inited = 0;
@@ -52,25 +51,15 @@ static void init_callback_code(void)
   callback_code_inited = 1;
 }
 
-#endif
-
 CAMLexport value caml_callbackN_exn(value closure, int narg, value args[])
 {
   int i;
   value res;
 
-  /* some alternate bytecode implementations (e.g. a JIT translator)
-     might require that the bytecode is kept in a local variable on
-     the C stack */
-#ifdef LOCAL_CALLBACK_BYTECODE
-  opcode_t local_callback_code[7];
-#endif
-
   CAMLassert(narg + 4 <= 256);
 
   Caml_state->extern_sp -= narg + 4;
   for (i = 0; i < narg; i++) Caml_state->extern_sp[i] = args[i]; /* arguments */
-#ifndef LOCAL_CALLBACK_BYTECODE
   Caml_state->extern_sp[narg] = (value)(callback_code + 4); /* return address */
   Caml_state->extern_sp[narg + 1] = Val_unit;    /* environment */
   Caml_state->extern_sp[narg + 2] = Val_long(0); /* extra args */
@@ -79,27 +68,6 @@ CAMLexport value caml_callbackN_exn(value closure, int narg, value args[])
   callback_code[1] = narg + 3;
   callback_code[3] = narg;
   res = caml_interprete(callback_code, sizeof(callback_code));
-#else /*have LOCAL_CALLBACK_BYTECODE*/
-  /* return address */
-  Caml_state->extern_sp[narg] = (value) (local_callback_code + 4);
-  Caml_state->extern_sp[narg + 1] = Val_unit;    /* environment */
-  Caml_state->extern_sp[narg + 2] = Val_long(0); /* extra args */
-  Caml_state->extern_sp[narg + 3] = closure;
-  local_callback_code[0] = ACC;
-  local_callback_code[1] = narg + 3;
-  local_callback_code[2] = APPLY;
-  local_callback_code[3] = narg;
-  local_callback_code[4] = POP;
-  local_callback_code[5] =  1;
-  local_callback_code[6] = STOP;
-  /* Not registering the code fragment, as code fragment management
-     would need to be revised thoroughly for an hypothetical JIT */
-#ifdef THREADED_CODE
-  caml_thread_code(local_callback_code, sizeof(local_callback_code));
-#endif /*THREADED_CODE*/
-  res = caml_interprete(local_callback_code, sizeof(local_callback_code));
-  caml_release_bytecode(local_callback_code, sizeof(local_callback_code));
-#endif /*LOCAL_CALLBACK_BYTECODE*/
   if (Is_exception_result(res)) Caml_state->extern_sp += narg + 4; /* PR#3419 */
   return res;
 }

runtime/caml/config.h

@@ -166,7 +166,7 @@ typedef uint64_t uintnat;
    as first-class values (GCC 2.x). */
 
 #if defined(__GNUC__) && __GNUC__ >= 2 && !defined(DEBUG) \
-    && !defined (SHRINKED_GNUC) && !defined(CAML_JIT)
+    && !defined (SHRINKED_GNUC)
 #define THREADED_CODE
 #endif
 

runtime/caml/interp.h

@@ -26,12 +26,6 @@
 /* interpret a bytecode */
 value caml_interprete (code_t prog, asize_t prog_size);
 
-/* tell the runtime that a bytecode program might be needed */
-void caml_prepare_bytecode(code_t prog, asize_t prog_size);
-
-/* tell the runtime that a bytecode program is no more needed */
-void caml_release_bytecode(code_t prog, asize_t prog_size);
-
 #endif /* CAML_INTERNALS */
 
 #endif /* CAML_INTERP_H */

runtime/interp.c

@@ -1082,10 +1082,6 @@ value caml_interprete(code_t prog, asize_t prog_size)
 
 #define Lookup(obj, lab) Field (Field (obj, 0), Int_val(lab))
 
-      /* please don't forget to keep below code in sync with the
-         functions caml_cache_public_method and
-         caml_cache_public_method2 in obj.c */
-
     Instruct(GETMETHOD):
       accu = Lookup(sp[0], accu);
       Next;
@@ -1182,20 +1178,3 @@ value caml_interprete(code_t prog, asize_t prog_size)
   }
 #endif
 }
-
-void caml_prepare_bytecode(code_t prog, asize_t prog_size) {
-  /* other implementations of the interpreter (such as an hypothetical
-     JIT translator) might want to do something with a bytecode before
-     running it */
-  CAMLassert(prog);
-  CAMLassert(prog_size>0);
-  /* actually, the threading of the bytecode might be done here */
-}
-
-void caml_release_bytecode(code_t prog, asize_t prog_size) {
-  /* other implementations of the interpreter (such as an hypothetical
-     JIT translator) might want to know when a bytecode is removed */
-  /* check that we have a program */
-  CAMLassert(prog);
-  CAMLassert(prog_size>0);
-}

runtime/meta.c

@@ -120,7 +120,6 @@ CAMLprim value caml_reify_bytecode(value ls_prog,
 #ifdef THREADED_CODE
   caml_thread_code((code_t) prog, len);
 #endif
-  caml_prepare_bytecode((code_t) prog, len);
 
   /* Notify debugger after fragment gets added and reified. */
   caml_debugger(CODE_LOADED, Val_long(fragnum));
@@ -138,17 +137,14 @@ CAMLprim value caml_reify_bytecode(value ls_prog,
 }
 
 /* signal to the interpreter machinery that a bytecode is no more
-   needed (before freeing it) - this might be useful for a JIT
+   needed (before freeing it) */
-   implementation */
 
 CAMLprim value caml_static_release_bytecode(value bc)
 {
   code_t prog;
-  asize_t len;
   struct code_fragment *cf;
 
   prog = Bytecode_val(bc)->prog;
-  len = Bytecode_val(bc)->len;
   caml_remove_debug_info(prog);
 
   cf = caml_find_code_fragment_by_pc((char *) prog);
@@ -159,11 +155,6 @@ CAMLprim value caml_static_release_bytecode(value bc)
 
   caml_remove_code_fragment(cf);
 
-#ifndef NATIVE_CODE
-  caml_release_bytecode(prog, len);
-#else
-  caml_failwith("Meta.static_release_bytecode impossible with native code");
-#endif
   caml_stat_free(prog);
   return Val_unit;
 }

runtime/obj.c

@@ -276,44 +276,6 @@ CAMLprim value caml_get_public_method (value obj, value tag)
   return (tag == Field(meths,li) ? Field (meths, li-1) : 0);
 }
 
-/* these two functions might be useful to an hypothetical JIT */
-
-#ifdef CAML_JIT
-#ifdef NATIVE_CODE
-#define MARK 1
-#else
-#define MARK 0
-#endif
-value caml_cache_public_method (value meths, value tag, value *cache)
-{
-  int li = 3, hi = Field(meths,0), mi;
-  while (li < hi) {
-    mi = ((li+hi) >> 1) | 1;
-    if (tag < Field(meths,mi)) hi = mi-2;
-    else li = mi;
-  }
-  *cache = (li-3)*sizeof(value) + MARK;
-  return Field (meths, li-1);
-}
-
-value caml_cache_public_method2 (value *meths, value tag, value *cache)
-{
-  value ofs = *cache & meths[1];
-  if (*(value*)(((char*)(meths+3)) + ofs - MARK) == tag)
-    return *(value*)(((char*)(meths+2)) + ofs - MARK);
-  {
-    int li = 3, hi = meths[0], mi;
-    while (li < hi) {
-      mi = ((li+hi) >> 1) | 1;
-      if (tag < meths[mi]) hi = mi-2;
-      else li = mi;
-    }
-    *cache = (li-3)*sizeof(value) + MARK;
-    return meths[li-1];
-  }
-}
-#endif /*CAML_JIT*/
-
 static value oo_last_id = Val_int(0);
 
 CAMLprim value caml_set_oo_id (value obj) {