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py/parse: Add code to fold logical constants in or/and/not operations.

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Adds about 200 bytes to the code size when constant folding is enabled.
This commit is contained in:
Damien George 2016-11-13 15:36:49 +11:00
parent ed9c93f0f1
commit 9b525134d1
1 changed files with 61 additions and 0 deletions
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61
py/parse.c
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@ -470,6 +470,63 @@ STATIC MP_DEFINE_CONST_MAP(mp_constants_map, mp_constants_table);
STATIC void push_result_rule(parser_t *parser, size_t src_line, const rule_t *rule, size_t num_args);
#if MICROPY_COMP_CONST_FOLDING
STATIC bool fold_logical_constants(parser_t *parser, const rule_t *rule, size_t *num_args) {
if (rule->rule_id == RULE_or_test
|| rule->rule_id == RULE_and_test) {
// folding for binary logical ops: or and
size_t copy_to = *num_args;
for (size_t i = copy_to; i > 0;) {
mp_parse_node_t pn = peek_result(parser, --i);
parser->result_stack[parser->result_stack_top - copy_to] = pn;
if (i == 0) {
// always need to keep the last value
break;
}
if (rule->rule_id == RULE_or_test) {
if (mp_parse_node_is_const_true(pn)) {
//
break;
} else if (!mp_parse_node_is_const_false(pn)) {
copy_to -= 1;
}
} else {
// RULE_and_test
if (mp_parse_node_is_const_false(pn)) {
break;
} else if (!mp_parse_node_is_const_true(pn)) {
copy_to -= 1;
}
}
}
copy_to -= 1; // copy_to now contains number of args to pop
// pop and discard all the short-circuited expressions
for (size_t i = 0; i < copy_to; ++i) {
pop_result(parser);
}
*num_args -= copy_to;
// we did a complete folding if there's only 1 arg left
return *num_args == 1;
} else if (rule->rule_id == RULE_not_test_2) {
// folding for unary logical op: not
mp_parse_node_t pn = peek_result(parser, 0);
if (mp_parse_node_is_const_false(pn)) {
pn = mp_parse_node_new_leaf(MP_PARSE_NODE_TOKEN, MP_TOKEN_KW_TRUE);
} else if (mp_parse_node_is_const_true(pn)) {
pn = mp_parse_node_new_leaf(MP_PARSE_NODE_TOKEN, MP_TOKEN_KW_FALSE);
} else {
return false;
}
pop_result(parser);
push_result_node(parser, pn);
return true;
}
return false;
}
STATIC bool fold_constants(parser_t *parser, const rule_t *rule, size_t num_args) {
// this code does folding of arbitrary integer expressions, eg 1 + 2 * 3 + 4
// it does not do partial folding, eg 1 + 2 + x -> 3 + x
@ -677,6 +734,10 @@ STATIC void push_result_rule(parser_t *parser, size_t src_line, const rule_t *ru
}
#if MICROPY_COMP_CONST_FOLDING
if (fold_logical_constants(parser, rule, &num_args)) {
// we folded this rule so return straight away
return;
}
if (fold_constants(parser, rule, num_args)) {
// we folded this rule so return straight away
return;