py: Add more compiler optimisations for constant if/while conditions.
diff --git a/py/compile.c b/py/compile.c
index 2c44fc4..61b8278 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -603,12 +603,13 @@
}
STATIC bool node_is_const_false(mp_parse_node_t pn) {
- return MP_PARSE_NODE_IS_TOKEN_KIND(pn, MP_TOKEN_KW_FALSE);
- // untested: || (MP_PARSE_NODE_IS_SMALL_INT(pn) && MP_PARSE_NODE_LEAF_SMALL_INT(pn) == 0);
+ return MP_PARSE_NODE_IS_TOKEN_KIND(pn, MP_TOKEN_KW_FALSE)
+ || (MP_PARSE_NODE_IS_SMALL_INT(pn) && MP_PARSE_NODE_LEAF_SMALL_INT(pn) == 0);
}
STATIC bool node_is_const_true(mp_parse_node_t pn) {
- return MP_PARSE_NODE_IS_TOKEN_KIND(pn, MP_TOKEN_KW_TRUE) || (MP_PARSE_NODE_IS_SMALL_INT(pn) && MP_PARSE_NODE_LEAF_SMALL_INT(pn) == 1);
+ return MP_PARSE_NODE_IS_TOKEN_KIND(pn, MP_TOKEN_KW_TRUE)
+ || (MP_PARSE_NODE_IS_SMALL_INT(pn) && MP_PARSE_NODE_LEAF_SMALL_INT(pn) != 0);
}
#if MICROPY_EMIT_CPYTHON
@@ -1658,25 +1659,31 @@
uint l_end = comp_next_label(comp);
- uint l_fail = comp_next_label(comp);
- c_if_cond(comp, pns->nodes[0], false, l_fail); // if condition
+ // optimisation: don't emit anything when "if False" (not in CPython)
+ if (MICROPY_EMIT_CPYTHON || !node_is_const_false(pns->nodes[0])) {
+ uint l_fail = comp_next_label(comp);
+ c_if_cond(comp, pns->nodes[0], false, l_fail); // if condition
- compile_node(comp, pns->nodes[1]); // if block
+ compile_node(comp, pns->nodes[1]); // if block
- if (
-#if !MICROPY_EMIT_CPYTHON
- // optimisation to not jump over non-existent elif/else blocks (this optimisation is not in CPython)
- !(MP_PARSE_NODE_IS_NULL(pns->nodes[2]) && MP_PARSE_NODE_IS_NULL(pns->nodes[3])) &&
-#endif
- // optimisation to not jump if last instruction was return
- !EMIT(last_emit_was_return_value)
- ) {
- // jump over elif/else blocks
- EMIT_ARG(jump, l_end);
+ // optimisation: skip everything else when "if True" (not in CPython)
+ if (!MICROPY_EMIT_CPYTHON && node_is_const_true(pns->nodes[0])) {
+ goto done;
+ }
+
+ if (
+ // optimisation: don't jump over non-existent elif/else blocks (not in CPython)
+ (MICROPY_EMIT_CPYTHON || !(MP_PARSE_NODE_IS_NULL(pns->nodes[2]) && MP_PARSE_NODE_IS_NULL(pns->nodes[3])))
+ // optimisation: don't jump if last instruction was return
+ && !EMIT(last_emit_was_return_value)
+ ) {
+ // jump over elif/else blocks
+ EMIT_ARG(jump, l_end);
+ }
+
+ EMIT_ARG(label_assign, l_fail);
}
- EMIT_ARG(label_assign, l_fail);
-
// compile elif blocks (if any)
mp_parse_node_t *pn_elif;
int n_elif = list_get(&pns->nodes[2], PN_if_stmt_elif_list, &pn_elif);
@@ -1684,19 +1691,30 @@
assert(MP_PARSE_NODE_IS_STRUCT_KIND(pn_elif[i], PN_if_stmt_elif)); // should be
mp_parse_node_struct_t *pns_elif = (mp_parse_node_struct_t*)pn_elif[i];
- l_fail = comp_next_label(comp);
- c_if_cond(comp, pns_elif->nodes[0], false, l_fail); // elif condition
+ // optimisation: don't emit anything when "if False" (not in CPython)
+ if (MICROPY_EMIT_CPYTHON || !node_is_const_false(pns_elif->nodes[0])) {
+ uint l_fail = comp_next_label(comp);
+ c_if_cond(comp, pns_elif->nodes[0], false, l_fail); // elif condition
- compile_node(comp, pns_elif->nodes[1]); // elif block
- if (!EMIT(last_emit_was_return_value)) { // simple optimisation to align with CPython
- EMIT_ARG(jump, l_end);
+ compile_node(comp, pns_elif->nodes[1]); // elif block
+
+ // optimisation: skip everything else when "elif True" (not in CPython)
+ if (!MICROPY_EMIT_CPYTHON && node_is_const_true(pns_elif->nodes[0])) {
+ goto done;
+ }
+
+ // optimisation: don't jump if last instruction was return
+ if (!EMIT(last_emit_was_return_value)) {
+ EMIT_ARG(jump, l_end);
+ }
+ EMIT_ARG(label_assign, l_fail);
}
- EMIT_ARG(label_assign, l_fail);
}
// compile else block
compile_node(comp, pns->nodes[3]); // can be null
+done:
EMIT_ARG(label_assign, l_end);
}
@@ -1735,12 +1753,16 @@
EMIT(pop_block);
}
#else
- uint top_label = comp_next_label(comp);
- EMIT_ARG(jump, continue_label);
- EMIT_ARG(label_assign, top_label);
- compile_node(comp, pns->nodes[1]); // body
- EMIT_ARG(label_assign, continue_label);
- c_if_cond(comp, pns->nodes[0], true, top_label); // condition
+ if (!node_is_const_false(pns->nodes[0])) { // optimisation: don't emit anything for "while False"
+ uint top_label = comp_next_label(comp);
+ if (!node_is_const_true(pns->nodes[0])) { // optimisation: don't jump to cond for "while True"
+ EMIT_ARG(jump, continue_label);
+ }
+ EMIT_ARG(label_assign, top_label);
+ compile_node(comp, pns->nodes[1]); // body
+ EMIT_ARG(label_assign, continue_label);
+ c_if_cond(comp, pns->nodes[0], true, top_label); // condition
+ }
#endif
// break/continue apply to outer loop (if any) in the else block