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decompiler: detect and turn inverse mult to div

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This commit is contained in:
ManDude
2024-07-17 21:55:14 +01:00
committed by Hat Kid
parent 8690104ba0
commit c3067c37ef
8 changed files with 127 additions and 3 deletions
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decompiler/IR2/FormExpressionAnalysis.cpp
+58 -1
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@@ -965,7 +965,7 @@ FormElement* make_and_compact_math_op(Form* arg0,
/*!
* Update a two-argument form that uses two floats.
* This is for operations like * and + that can be nested
* (* (* a b)) -> (* a b c)
* (* (* a b) c) -> (* a b c)
* Note that we only apply this to the _first_ argument to keep the order of operations the same.
*/
void SimpleExpressionElement::update_from_stack_float_2_nestable(const Env& env,
@@ -2603,6 +2603,9 @@ void SetVarElement::push_to_stack(const Env& env, FormPool& pool, FormStack& sta
ASSERT(x->parent_form == m_src);
}
if (auto test0 = m_src->to_string(env) == "(* 0.00024414062 (-> arg0 y))") {
printf("");
}
if (m_src->is_single_element()) {
auto src_as_se = dynamic_cast<SimpleExpressionElement*>(m_src->back());
if (src_as_se) {
@@ -2624,6 +2627,60 @@ void SetVarElement::push_to_stack(const Env& env, FormPool& pool, FormStack& sta
}
}
}
// (* 0.125 b) -> (/ b 8)
// adds explicit cast b to float if necessary
auto src_as_ge = dynamic_cast<GenericElement*>(m_src->back());
if (src_as_ge) {
auto mr = match(Matcher::op_fixed(FixedOperatorKind::MULTIPLICATION,
{Matcher::any_single(0), Matcher::any(1)}),
m_src);
if (mr.matched && std::abs(mr.maps.floats.at(0)) < 1 && mr.maps.floats.at(0) != 0) {
float divisor_num = 1.0f / mr.maps.floats.at(0);
int divisor_int = (int)divisor_num;
// note: for some reason 0.016666668 shows up constantly where 1/60 should be. we won't
// force it to 60, but we will transform it anyway
if (divisor_int == divisor_num || mr.maps.floats.at(0) == 0.016666668f) {
auto elt = mr.maps.forms.at(1)->try_as_single_element();
auto b_as_simple = dynamic_cast<SimpleExpressionElement*>(elt);
// WARNING : there is an assumption here that derefs DO NOT have implicit casts!
auto b_as_deref = dynamic_cast<DerefElement*>(elt);
if (b_as_deref ||
(b_as_simple && b_as_simple->expr().kind() == SimpleExpression::Kind::IDENTITY)) {
// TODO check if op is float, cast if so
Form* divisor = nullptr;
if (divisor_num == 4096.0f) {
divisor = pool.form<ConstantTokenElement>("METER_LENGTH");
} else if (divisor_num == (float)divisor_int && divisor_int % 2048 == 0) {
divisor = pool.form<GenericElement>(
GenericOperator::make_function(pool.form<ConstantTokenElement>("meters")),
divisor_int % (int)METER_LENGTH
? pool.form<ConstantFloatElement>(divisor_num / (float)METER_LENGTH)
: pool.form<SimpleAtomElement>(divisor_int / 4096, true));
} else if (divisor_num == divisor_int) {
divisor = pool.form<SimpleAtomElement>(divisor_int, true);
} else {
// this shouldn't run because of the checks before.
divisor = pool.form<ConstantFloatElement>(divisor_num);
}
if (divisor) {
if (b_as_deref || (env.get_types_before_op(b_as_simple->expr().var().idx())
.get(b_as_simple->expr().var().reg())
.typespec() == TypeSpec("float"))) {
*m_src->back_ref() = pool.alloc_element<GenericElement>(
GenericOperator::make_fixed(FixedOperatorKind::DIVISION), mr.maps.forms.at(1),
divisor);
} else {
*m_src->back_ref() = pool.alloc_element<GenericElement>(
GenericOperator::make_fixed(FixedOperatorKind::DIVISION),
pool.form<CastElement>(TypeSpec("float"), mr.maps.forms.at(1), true), divisor);
}
m_src->back()->parent_form = m_src;
}
}
}
}
}
}
stack.push_value_to_reg(m_dst, m_src, true, m_src_type, m_var_info);