py: Reuse value stack in VM WITH_CLEANUP opcode to reduce C-stack size.
Saves 8 bytes C-stack on stmhal and 16 bytes on unix x86.
diff --git a/py/vm.c b/py/vm.c
index 587948f..c1a7814 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -587,25 +587,32 @@
assert(0);
}
} else if (mp_obj_is_exception_type(TOP())) {
- mp_obj_t args[3] = {sp[0], sp[-1], sp[-2]};
- mp_obj_t ret_value = mp_call_function_n_kw(sp[-3], 3, 0, args);
- // Pop __exit__ boundmethod at sp[-3]
- // TODO: Once semantics is proven, optimize for case when ret_value == True
- sp[-3] = sp[-2];
- sp[-2] = sp[-1];
- sp[-1] = sp[0];
- sp--;
+ // Need to pass (sp[0], sp[-1], sp[-2]) as arguments so must reverse the
+ // order of these on the value stack (don't want to create a temporary
+ // array because it increases stack footprint of the VM).
+ mp_obj_t obj = sp[-2];
+ sp[-2] = sp[0];
+ sp[0] = obj;
+ mp_obj_t ret_value = mp_call_function_n_kw(sp[-3], 3, 0, &sp[-2]);
if (mp_obj_is_true(ret_value)) {
// This is what CPython does
//PUSH(MP_OBJ_NEW_SMALL_INT(UNWIND_SILENCED));
// But what we need to do is - pop exception from value stack...
- sp -= 3;
+ sp -= 4;
// ... pop "with" exception handler, and signal END_FINALLY
// to just execute finally handler normally (by pushing None
// on value stack)
assert(exc_sp >= exc_stack);
POP_EXC_BLOCK();
PUSH(mp_const_none);
+ } else {
+ // Pop __exit__ boundmethod at sp[-3], remembering that top 3 values
+ // are reversed.
+ sp[-3] = sp[0];
+ obj = sp[-2];
+ sp[-2] = sp[-1];
+ sp[-1] = obj;
+ sp--;
}
} else {
assert(0);