py: Simplify bytecode prelude when encoding closed over variables.

py/bc.c

@@ -228,9 +228,10 @@ continue2:;
 
     // bytecode prelude: initialise closed over variables
     const byte *ip = code_state->ip;
-    for (mp_uint_t n_local = *ip++; n_local > 0; n_local--) {
-        mp_uint_t local_num = *ip++;
-        code_state->state[n_state - 1 - local_num] = mp_obj_new_cell(code_state->state[n_state - 1 - local_num]);
+    mp_uint_t local_num;
+    while ((local_num = *ip++) != 255) {
+        code_state->state[n_state - 1 - local_num] =
+            mp_obj_new_cell(code_state->state[n_state - 1 - local_num]);
     }
 
     // now that we skipped over the prelude, set the ip for the VM

py/emitbc.c

@@ -322,21 +322,14 @@ void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) {
     }
 
     // bytecode prelude: initialise closed over variables
-    int num_cell = 0;
-    for (int i = 0; i < scope->id_info_len; i++) {
-        id_info_t *id = &scope->id_info[i];
-        if (id->kind == ID_INFO_KIND_CELL) {
-            num_cell += 1;
-        }
-    }
-    assert(num_cell <= 255);
-    emit_write_bytecode_byte(emit, num_cell); // write number of locals that are cells
     for (int i = 0; i < scope->id_info_len; i++) {
         id_info_t *id = &scope->id_info[i];
         if (id->kind == ID_INFO_KIND_CELL) {
+            assert(id->local_num < 255);
             emit_write_bytecode_byte(emit, id->local_num); // write the local which should be converted to a cell
         }
     }
+    emit_write_bytecode_byte(emit, 255); // end of list sentinel
 }
 
 void mp_emit_bc_end_pass(emit_t *emit) {

py/showbc.c

@@ -95,10 +95,8 @@ void mp_bytecode_print(const void *descr, mp_uint_t n_total_args, const byte *ip
 
     // bytecode prelude: initialise closed over variables
     {
-        uint n_local = *ip++;
-        printf("(NUM_LOCAL %u)\n", n_local);
-        for (; n_local > 0; n_local--) {
-            uint local_num = *ip++;
+        uint local_num;
+        while ((local_num = *ip++) != 255) {
             printf("(INIT_CELL %u)\n", local_num);
         }
         len -= ip - mp_showbc_code_start;

tests/cmdline/cmd_showbc.py.exp

@@ -5,7 +5,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:
 (N_STATE 3)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-3 line=1
 ########
   bc=\\d\+ line=134
@@ -32,7 +31,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:
 (N_STATE 25)
 (N_EXC_STACK 2)
-(NUM_LOCAL 3)
 (INIT_CELL 14)
 (INIT_CELL 15)
 (INIT_CELL 16)
@@ -304,7 +302,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names: a
 (N_STATE 5)
 (N_EXC_STACK 0)
-(NUM_LOCAL 1)
 (INIT_CELL 0)
 ########
   bc=\\d\+ line=124
@@ -323,7 +320,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:
 (N_STATE 2)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-3 line=1
   bc=0 line=129
   bc=3 line=130
@@ -348,7 +344,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:
 (N_STATE 1)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-3 line=1
   bc=10 line=135
 00 LOAD_NAME __name__ (cache=0)
@@ -364,7 +359,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:  c e
 (N_STATE 6)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-\\d\+ line=1
 00 LOAD_FAST 2
 01 FOR_ITER 17
@@ -384,7 +378,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:  c e
 (N_STATE 7)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-\\d\+ line=1
 00 BUILD_LIST 0
 02 LOAD_FAST 2
@@ -403,7 +396,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:  c e
 (N_STATE 8)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-\\d\+ line=1
 ########
 00 BUILD_MAP 0
@@ -424,7 +416,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names: x
 (N_STATE 4)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-\\d\+ line=1
 ########
   bc=\\d\+ line=105
@@ -444,7 +435,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names: b a
 (N_STATE 4)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-\\d\+ line=1
 ########
   bc=\\d\+ line=125

tests/cmdline/cmd_verbose.py.exp

@@ -7,7 +7,6 @@ Raw bytecode (code_info_size=\\d\+, bytecode_size=\\d\+):
 arg names:
 (N_STATE 2)
 (N_EXC_STACK 0)
-(NUM_LOCAL 0)
   bc=-3 line=1
   bc=0 line=3
 00 LOAD_NAME print (cache=0)