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py: Reuse value stack in VM WITH_CLEANUP opcode to reduce C-stack size.

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Saves 8 bytes C-stack on stmhal and 16 bytes on unix x86.
This commit is contained in:
Damien George 2015-02-10 13:21:42 +00:00
parent ea0461dcd3
commit 596f41da04
1 changed files with 16 additions and 9 deletions
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25
py/vm.c
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@ -587,25 +587,32 @@ dispatch_loop:
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);