py: Provide mp_decode_uint_skip() to help reduce stack usage.
Taking the address of a local variable leads to increased stack usage, so the mp_decode_uint_skip() function is added to reduce the need for taking addresses. The changes in this patch reduce stack usage of a Python call by 8 bytes on ARM Thumb, by 16 bytes on non-windowing Xtensa archs, and by 16 bytes on x86-64. Code size is also slightly reduced on most archs by around 32 bytes.
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10
py/bc.c
10
py/bc.c
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@ -64,6 +64,14 @@ mp_uint_t mp_decode_uint_value(const byte *ptr) {
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return mp_decode_uint(&ptr);
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}
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// This function is used to help reduce stack usage at the caller, for the case when
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// the caller doesn't need the actual value and just wants to skip over it.
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const byte *mp_decode_uint_skip(const byte *ptr) {
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while ((*ptr++) & 0x80) {
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}
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return ptr;
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}
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STATIC NORETURN void fun_pos_args_mismatch(mp_obj_fun_bc_t *f, size_t expected, size_t given) {
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#if MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE
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// generic message, used also for other argument issues
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@ -115,7 +123,7 @@ void mp_setup_code_state(mp_code_state_t *code_state, size_t n_args, size_t n_kw
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// get params
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size_t n_state = mp_decode_uint(&code_state->ip);
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mp_decode_uint(&code_state->ip); // skip n_exc_stack
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code_state->ip = mp_decode_uint_skip(code_state->ip); // skip n_exc_stack
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size_t scope_flags = *code_state->ip++;
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size_t n_pos_args = *code_state->ip++;
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size_t n_kwonly_args = *code_state->ip++;
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1
py/bc.h
1
py/bc.h
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@ -92,6 +92,7 @@ typedef struct _mp_code_state_t {
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mp_uint_t mp_decode_uint(const byte **ptr);
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mp_uint_t mp_decode_uint_value(const byte *ptr);
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const byte *mp_decode_uint_skip(const byte *ptr);
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mp_vm_return_kind_t mp_execute_bytecode(mp_code_state_t *code_state, volatile mp_obj_t inject_exc);
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mp_code_state_t *mp_obj_fun_bc_prepare_codestate(mp_obj_t func, size_t n_args, size_t n_kw, const mp_obj_t *args);
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22
py/objfun.c
22
py/objfun.c
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@ -141,11 +141,11 @@ const mp_obj_type_t mp_type_fun_builtin_var = {
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/* byte code functions */
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qstr mp_obj_code_get_name(const byte *code_info) {
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mp_decode_uint(&code_info); // skip code_info_size entry
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code_info = mp_decode_uint_skip(code_info); // skip code_info_size entry
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#if MICROPY_PERSISTENT_CODE
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return code_info[0] | (code_info[1] << 8);
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#else
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return mp_decode_uint(&code_info);
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return mp_decode_uint_value(code_info);
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#endif
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}
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@ -163,8 +163,8 @@ qstr mp_obj_fun_get_name(mp_const_obj_t fun_in) {
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#endif
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const byte *bc = fun->bytecode;
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mp_decode_uint(&bc); // skip n_state
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mp_decode_uint(&bc); // skip n_exc_stack
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bc = mp_decode_uint_skip(bc); // skip n_state
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bc = mp_decode_uint_skip(bc); // skip n_exc_stack
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bc++; // skip scope_params
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bc++; // skip n_pos_args
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bc++; // skip n_kwonly_args
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@ -205,12 +205,9 @@ mp_code_state_t *mp_obj_fun_bc_prepare_codestate(mp_obj_t self_in, size_t n_args
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MP_STACK_CHECK();
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mp_obj_fun_bc_t *self = MP_OBJ_TO_PTR(self_in);
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// get start of bytecode
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const byte *ip = self->bytecode;
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// bytecode prelude: state size and exception stack size
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size_t n_state = mp_decode_uint(&ip);
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size_t n_exc_stack = mp_decode_uint(&ip);
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size_t n_state = mp_decode_uint_value(self->bytecode);
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size_t n_exc_stack = mp_decode_uint_value(mp_decode_uint_skip(self->bytecode));
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// allocate state for locals and stack
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size_t state_size = n_state * sizeof(mp_obj_t) + n_exc_stack * sizeof(mp_exc_stack_t);
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@ -243,12 +240,9 @@ STATIC mp_obj_t fun_bc_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const
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mp_obj_fun_bc_t *self = MP_OBJ_TO_PTR(self_in);
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DEBUG_printf("Func n_def_args: %d\n", self->n_def_args);
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// get start of bytecode
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const byte *ip = self->bytecode;
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// bytecode prelude: state size and exception stack size
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size_t n_state = mp_decode_uint(&ip);
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size_t n_exc_stack = mp_decode_uint(&ip);
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size_t n_state = mp_decode_uint_value(self->bytecode);
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size_t n_exc_stack = mp_decode_uint_value(mp_decode_uint_skip(self->bytecode));
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#if VM_DETECT_STACK_OVERFLOW
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n_state += 1;
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@ -54,12 +54,9 @@ STATIC mp_obj_t gen_wrap_call(mp_obj_t self_in, size_t n_args, size_t n_kw, cons
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mp_obj_fun_bc_t *self_fun = (mp_obj_fun_bc_t*)self->fun;
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assert(self_fun->base.type == &mp_type_fun_bc);
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// get start of bytecode
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const byte *ip = self_fun->bytecode;
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// bytecode prelude: get state size and exception stack size
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mp_uint_t n_state = mp_decode_uint(&ip);
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mp_uint_t n_exc_stack = mp_decode_uint(&ip);
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size_t n_state = mp_decode_uint_value(self_fun->bytecode);
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size_t n_exc_stack = mp_decode_uint_value(mp_decode_uint_skip(self_fun->bytecode));
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// allocate the generator object, with room for local stack and exception stack
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mp_obj_gen_instance_t *o = m_new_obj_var(mp_obj_gen_instance_t, byte,
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13
py/vm.c
13
py/vm.c
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@ -1363,22 +1363,25 @@ unwind_loop:
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// TODO need a better way of not adding traceback to constant objects (right now, just GeneratorExit_obj and MemoryError_obj)
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if (nlr.ret_val != &mp_const_GeneratorExit_obj && nlr.ret_val != &mp_const_MemoryError_obj) {
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const byte *ip = code_state->fun_bc->bytecode;
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mp_decode_uint(&ip); // skip n_state
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mp_decode_uint(&ip); // skip n_exc_stack
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ip = mp_decode_uint_skip(ip); // skip n_state
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ip = mp_decode_uint_skip(ip); // skip n_exc_stack
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ip++; // skip scope_params
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ip++; // skip n_pos_args
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ip++; // skip n_kwonly_args
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ip++; // skip n_def_pos_args
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size_t bc = code_state->ip - ip;
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size_t code_info_size = mp_decode_uint(&ip);
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size_t code_info_size = mp_decode_uint_value(ip);
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ip = mp_decode_uint_skip(ip); // skip code_info_size
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bc -= code_info_size;
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#if MICROPY_PERSISTENT_CODE
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qstr block_name = ip[0] | (ip[1] << 8);
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qstr source_file = ip[2] | (ip[3] << 8);
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ip += 4;
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#else
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qstr block_name = mp_decode_uint(&ip);
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qstr source_file = mp_decode_uint(&ip);
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qstr block_name = mp_decode_uint_value(ip);
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ip = mp_decode_uint_skip(ip);
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qstr source_file = mp_decode_uint_value(ip);
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ip = mp_decode_uint_skip(ip);
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#endif
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size_t source_line = 1;
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size_t c;
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