Commit 391db866 authored by Damien George's avatar Damien George
Browse files

py: Add more compiler optimisations for constant if/while conditions.

parent 235f9b33
......@@ -603,12 +603,13 @@ void compile_generic_tuple(compiler_t *comp, mp_parse_node_struct_t *pns) {
}
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
......@@ -1658,24 +1659,30 @@ void compile_if_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
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;
}
EMIT_ARG(label_assign, l_fail);
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);
}
// compile elif blocks (if any)
mp_parse_node_t *pn_elif;
......@@ -1684,19 +1691,30 @@ void compile_if_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
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 @@ void compile_while_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
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
......
# test if conditions which are optimised by the compiler
if 0:
print(5)
else:
print(6)
if 1:
print(7)
if 2:
print(8)
if -1:
print(9)
elif 1:
print(10)
if 0:
print(11)
else:
print(12)
if 0:
print(13)
elif 1:
print(14)
if 0:
print(15)
elif 0:
print(16)
else:
print(17)
f2 = 0
def f(t1, t2, f1):
......
# test while conditions which are optimised by the compiler
while 0:
print(0)
else:
print(1)
while 1:
print(2)
break
while 2:
print(3)
break
while -1:
print(4)
break
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