py: Merge mp_execute_bytecode into fun_bc_call.

This reduces stack usage by 16 words (64 bytes) for stmhal/ port.

See issue #640.

py/bc.h

@@ -49,8 +49,7 @@ typedef struct _mp_code_state {
     //mp_exc_stack_t exc_state[0];
 } mp_code_state;
 
-mp_vm_return_kind_t mp_execute_bytecode(const byte *code, const mp_obj_t *args, uint n_args, const mp_obj_t *args2, uint n_args2, mp_obj_t *ret);
-mp_vm_return_kind_t mp_execute_bytecode2(mp_code_state *code_state, volatile mp_obj_t inject_exc);
+mp_vm_return_kind_t mp_execute_bytecode(mp_code_state *code_state, volatile mp_obj_t inject_exc);
 void mp_bytecode_print(const void *descr, const byte *code, int len);
 void mp_bytecode_print2(const byte *code, int len);
 

py/objfun.c

@@ -237,6 +237,14 @@ arg_error:
     fun_pos_args_mismatch(self, self->n_pos_args, n_args);
 }
 
+// With this macro you can tune the maximum number of function state bytes
+// that will be allocated on the stack.  Any function that needs more
+// than this will use the heap.
+#define VM_MAX_STATE_ON_STACK (10 * sizeof(machine_uint_t))
+
+// Set this to enable a simple stack overflow check.
+#define VM_DETECT_STACK_OVERFLOW (0)
+
 STATIC mp_obj_t fun_bc_call(mp_obj_t self_in, uint n_args, uint n_kw, const mp_obj_t *args) {
     // This function is pretty complicated.  It's main aim is to be efficient in speed and RAM
     // usage for the common case of positional only args.
@@ -379,7 +387,113 @@ continue2:;
     DEBUG_printf("Calling: args=%p, n_args=%d, extra_args=%p, n_extra_args=%d\n", args, n_args, extra_args, n_extra_args);
     dump_args(args, n_args);
     dump_args(extra_args, n_extra_args);
-    mp_vm_return_kind_t vm_return_kind = mp_execute_bytecode(self->bytecode, args, n_args, extra_args, n_extra_args, &result);
+
+    // At this point the args have all been processed and we are ready to
+    // execute the bytecode.  But we must first build the execution context.
+
+    const byte *ip = self->bytecode;
+
+    // get code info size, and skip line number table
+    machine_uint_t code_info_size = ip[0] | (ip[1] << 8) | (ip[2] << 16) | (ip[3] << 24);
+    ip += code_info_size;
+
+    // bytecode prelude: state size and exception stack size; 16 bit uints
+    machine_uint_t n_state = ip[0] | (ip[1] << 8);
+    machine_uint_t n_exc_stack = ip[2] | (ip[3] << 8);
+    ip += 4;
+
+    // allocate state for locals and stack
+#if VM_DETECT_STACK_OVERFLOW
+    n_state += 1;
+#endif
+
+    int state_size = n_state * sizeof(mp_obj_t) + n_exc_stack * sizeof(mp_exc_stack_t);
+    mp_code_state *code_state;
+    if (state_size > VM_MAX_STATE_ON_STACK) {
+        code_state = m_new_obj_var(mp_code_state, byte, state_size);
+    } else {
+        code_state = alloca(sizeof(mp_code_state) + state_size);
+    }
+
+    code_state->code_info = self->bytecode;
+    code_state->sp = &code_state->state[0] - 1;
+    code_state->exc_sp = (mp_exc_stack_t*)(code_state->state + n_state) - 1;
+    code_state->n_state = n_state;
+
+    // init args
+    for (uint i = 0; i < n_args; i++) {
+        code_state->state[n_state - 1 - i] = args[i];
+    }
+    for (uint i = 0; i < n_extra_args; i++) {
+        code_state->state[n_state - 1 - n_args - i] = extra_args[i];
+    }
+
+    // set rest of state to MP_OBJ_NULL
+    for (uint i = 0; i < n_state - n_args - n_extra_args; i++) {
+        code_state->state[i] = MP_OBJ_NULL;
+    }
+
+    // bytecode prelude: initialise closed over variables
+    for (uint n_local = *ip++; n_local > 0; n_local--) {
+        uint local_num = *ip++;
+        code_state->state[n_state - 1 - local_num] = mp_obj_new_cell(code_state->state[n_state - 1 - local_num]);
+    }
+
+    code_state->ip = ip;
+
+    // execute the byte code
+    mp_vm_return_kind_t vm_return_kind = mp_execute_bytecode(code_state, MP_OBJ_NULL);
+
+#if VM_DETECT_STACK_OVERFLOW
+    if (vm_return_kind == MP_VM_RETURN_NORMAL) {
+        if (code_state->sp < code_state->state) {
+            printf("VM stack underflow: " INT_FMT "\n", code_state->sp - code_state->state);
+            assert(0);
+        }
+    }
+    // We can't check the case when an exception is returned in state[n_state - 1]
+    // and there are no arguments, because in this case our detection slot may have
+    // been overwritten by the returned exception (which is allowed).
+    if (!(vm_return_kind == MP_VM_RETURN_EXCEPTION && n_args == 0 && n_extra_args == 0)) {
+        // Just check to see that we have at least 1 null object left in the state.
+        bool overflow = true;
+        for (uint i = 0; i < n_state - n_args - n_extra_args; i++) {
+            if (code_state->state[i] == MP_OBJ_NULL) {
+                overflow = false;
+                break;
+            }
+        }
+        if (overflow) {
+            printf("VM stack overflow state=%p n_state+1=" UINT_FMT "\n", code_state->state, n_state);
+            assert(0);
+        }
+    }
+#endif
+
+    switch (vm_return_kind) {
+        case MP_VM_RETURN_NORMAL:
+            // return value is in *sp
+            result = *code_state->sp;
+            break;
+
+        case MP_VM_RETURN_EXCEPTION:
+            // return value is in state[n_state - 1]
+            result = code_state->state[n_state - 1];
+            break;
+
+        case MP_VM_RETURN_YIELD: // byte-code shouldn't yield
+        default:
+            assert(0);
+            result = mp_const_none;
+            vm_return_kind = MP_VM_RETURN_NORMAL;
+            break;
+    }
+
+    // free the state if it was allocated on the heap
+    if (state_size > VM_MAX_STATE_ON_STACK) {
+        m_del_var(mp_code_state, byte, state_size, code_state);
+    }
+
     mp_globals_set(old_globals);
 
     if (vm_return_kind == MP_VM_RETURN_NORMAL) {

py/objgenerator.c

@@ -106,7 +106,7 @@ mp_vm_return_kind_t mp_obj_gen_resume(mp_obj_t self_in, mp_obj_t send_value, mp_
     }
     mp_obj_dict_t *old_globals = mp_globals_get();
     mp_globals_set(self->globals);
-    mp_vm_return_kind_t ret_kind = mp_execute_bytecode2(&self->code_state, throw_value);
+    mp_vm_return_kind_t ret_kind = mp_execute_bytecode(&self->code_state, throw_value);
     mp_globals_set(old_globals);
 
     switch (ret_kind) {
@@ -263,7 +263,7 @@ mp_obj_t mp_obj_new_gen_instance(mp_obj_dict_t *globals, const byte *bytecode,
     o->code_state.exc_sp = (mp_exc_stack_t*)(o->code_state.state + n_state) - 1;
     o->code_state.n_state = n_state;
 
-    // copy args to end of state array, in reverse (that's how mp_execute_bytecode2 needs it)
+    // copy args to end of state array, in reverse (that's how mp_execute_bytecode needs it)
     for (uint i = 0; i < n_args; i++) {
         o->code_state.state[n_state - 1 - i] = args[i];
     }

py/vm.c

@@ -41,12 +41,6 @@
 #include "bc.h"
 #include "objgenerator.h"
 
-// With these macros you can tune the maximum number of function state bytes
-// that will be allocated on the stack.  Any function that needs more
-// than this will use the heap.
-#define VM_MAX_STATE_ON_STACK (10 * sizeof(machine_uint_t))
-
-#define DETECT_VM_STACK_OVERFLOW (0)
 #if 0
 #define TRACE(ip) mp_bytecode_print2(ip, 1);
 #else
@@ -103,123 +97,13 @@ typedef enum {
     currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); /* restore previous state */ \
     exc_sp--; /* pop back to previous exception handler */
 
-mp_vm_return_kind_t mp_execute_bytecode(const byte *code, const mp_obj_t *args, uint n_args,
-                                                          const mp_obj_t *args2, uint n_args2, mp_obj_t *ret) {
-    const byte *ip = code;
-
-    // get code info size, and skip line number table
-    machine_uint_t code_info_size = ip[0] | (ip[1] << 8) | (ip[2] << 16) | (ip[3] << 24);
-    ip += code_info_size;
-
-    // bytecode prelude: state size and exception stack size; 16 bit uints
-    machine_uint_t n_state = ip[0] | (ip[1] << 8);
-    machine_uint_t n_exc_stack = ip[2] | (ip[3] << 8);
-    ip += 4;
-
-    // allocate state for locals and stack
-#if DETECT_VM_STACK_OVERFLOW
-    n_state += 1;
-#endif
-
-    int state_size = n_state * sizeof(mp_obj_t) + n_exc_stack * sizeof(mp_exc_stack_t);
-    mp_code_state *code_state;
-    if (state_size > VM_MAX_STATE_ON_STACK) {
-        code_state = m_new_obj_var(mp_code_state, byte, state_size);
-    } else {
-        code_state = alloca(sizeof(mp_code_state) + state_size);
-    }
-
-    code_state->code_info = code;
-    code_state->sp = &code_state->state[0] - 1;
-    code_state->exc_sp = (mp_exc_stack_t*)(code_state->state + n_state) - 1;
-    code_state->n_state = n_state;
-
-    // init args
-    for (uint i = 0; i < n_args; i++) {
-        code_state->state[n_state - 1 - i] = args[i];
-    }
-    for (uint i = 0; i < n_args2; i++) {
-        code_state->state[n_state - 1 - n_args - i] = args2[i];
-    }
-
-    // set rest of state to MP_OBJ_NULL
-    for (uint i = 0; i < n_state - n_args - n_args2; i++) {
-        code_state->state[i] = MP_OBJ_NULL;
-    }
-
-    // bytecode prelude: initialise closed over variables
-    for (uint n_local = *ip++; n_local > 0; n_local--) {
-        uint local_num = *ip++;
-        code_state->state[n_state - 1 - local_num] = mp_obj_new_cell(code_state->state[n_state - 1 - local_num]);
-    }
-
-    code_state->ip = ip;
-
-    // execute the byte code
-    mp_vm_return_kind_t vm_return_kind = mp_execute_bytecode2(code_state, MP_OBJ_NULL);
-
-#if DETECT_VM_STACK_OVERFLOW
-    if (vm_return_kind == MP_VM_RETURN_NORMAL) {
-        if (code_state->sp < code_state->state) {
-            printf("VM stack underflow: " INT_FMT "\n", code_state->sp - code_state->state);
-            assert(0);
-        }
-    }
-    // We can't check the case when an exception is returned in state[n_state - 1]
-    // and there are no arguments, because in this case our detection slot may have
-    // been overwritten by the returned exception (which is allowed).
-    if (!(vm_return_kind == MP_VM_RETURN_EXCEPTION && n_args == 0 && n_args2 == 0)) {
-        // Just check to see that we have at least 1 null object left in the state.
-        bool overflow = true;
-        for (uint i = 0; i < n_state - n_args - n_args2; i++) {
-            if (code_state->state[i] == MP_OBJ_NULL) {
-                overflow = false;
-                break;
-            }
-        }
-        if (overflow) {
-            printf("VM stack overflow state=%p n_state+1=" UINT_FMT "\n", code_state->state, n_state);
-            assert(0);
-        }
-    }
-#endif
-
-    mp_vm_return_kind_t ret_kind;
-    switch (vm_return_kind) {
-        case MP_VM_RETURN_NORMAL:
-            // return value is in *sp
-            *ret = *code_state->sp;
-            ret_kind = MP_VM_RETURN_NORMAL;
-            break;
-
-        case MP_VM_RETURN_EXCEPTION:
-            // return value is in state[n_state - 1]
-            *ret = code_state->state[n_state - 1];
-            ret_kind = MP_VM_RETURN_EXCEPTION;
-            break;
-
-        case MP_VM_RETURN_YIELD: // byte-code shouldn't yield
-        default:
-            assert(0);
-            *ret = mp_const_none;
-            ret_kind = MP_VM_RETURN_NORMAL;
-            break;
-    }
-
-    // free the state if it was allocated on the heap
-    if (state_size > VM_MAX_STATE_ON_STACK) {
-        m_del_var(mp_code_state, byte, state_size, code_state);
-    }
-    return ret_kind;
-}
-
 // fastn has items in reverse order (fastn[0] is local[0], fastn[-1] is local[1], etc)
 // sp points to bottom of stack which grows up
 // returns:
 //  MP_VM_RETURN_NORMAL, sp valid, return value in *sp
 //  MP_VM_RETURN_YIELD, ip, sp valid, yielded value in *sp
 //  MP_VM_RETURN_EXCEPTION, exception in fastn[0]
-mp_vm_return_kind_t mp_execute_bytecode2(mp_code_state *code_state, volatile mp_obj_t inject_exc) {
+mp_vm_return_kind_t mp_execute_bytecode(mp_code_state *code_state, volatile mp_obj_t inject_exc) {
 #if MICROPY_OPT_COMPUTED_GOTO
     #include "vmentrytable.h"
     #define DISPATCH() do { \
@@ -241,7 +125,7 @@ mp_vm_return_kind_t mp_execute_bytecode2(mp_code_state *code_state, volatile mp_
     // loop and the exception handler, leading to very obscure bugs.
     #define RAISE(o) do { nlr_pop(); nlr.ret_val = o; goto exception_handler; } while(0)
 
-    // Pointers which are constant for particular invocation of mp_execute_bytecode2()
+    // Pointers which are constant for particular invocation of mp_execute_bytecode()
     mp_obj_t *const fastn = &code_state->state[code_state->n_state - 1];
     mp_exc_stack_t *const exc_stack = (mp_exc_stack_t*)(code_state->state + code_state->n_state);