UsedVarsFixpointIterator::UsedVarsFixpointIterator(
const local_pointers::FixpointIterator& pointers_fp_iter,
const EffectSummaryMap& effect_summaries,
const std::unordered_set<const DexMethod*>& non_overridden_virtuals,
const cfg::ControlFlowGraph& cfg)
: MonotonicFixpointIterator(cfg, cfg.blocks().size()),
m_insn_env_map(gen_instruction_environment_map(cfg, pointers_fp_iter)),
m_effect_summaries(effect_summaries),
m_non_overridden_virtuals(non_overridden_virtuals) {}
boost::optional<ParamIndex> find_return_param_index(
cfg::ControlFlowGraph& cfg) {
for (auto& mie : InstructionIterable(cfg)) {
TRACE(RP, 2, " %s\n", SHOW(mie.insn));
}
// find register that is being returned (if any)
cfg.calculate_exit_block();
auto exit_block = cfg.exit_block();
auto it = exit_block->rbegin();
if (it == exit_block->rend() || !is_return_value(it->insn->opcode()))
return boost::none;
auto return_reg = it->insn->src(0);
TRACE(RP, 2, " returns v%d\n", return_reg);
++it;
if (it == exit_block->rend() || !is_move(it->insn->opcode()))
return boost::none;
auto src_reg = it->insn->src(0);
TRACE(RP, 2, " move v%d, v%d\n", it->insn->dest(), src_reg);
if (it->insn->dest() != return_reg) return boost::none;
// let's see if it came from a unique load-param
IRInstruction* load_param = nullptr;
for (auto& mie : InstructionIterable(cfg)) {
if (mie.insn->dests_size()) {
if (mie.insn->dest() == src_reg) {
if (opcode::is_load_param(mie.insn->opcode())) {
load_param = mie.insn;
} else {
TRACE(RP, 2, " move_reg clobbered\n");
return boost::none;
}
}
}
}
if (load_param != nullptr) {
ParamIndex param_index = get_load_param_map(cfg).at(load_param);
TRACE(RP, 2, " found matching load-param %d\n", param_index);
return param_index;
} else {
TRACE(RP, 2, " did not find matching load-param\n");
return boost::none;
}
}
/*
* Record the environment before the execution of every instruction. We need
* this data during the backwards used vars analysis.
*/
static std::unordered_map<const IRInstruction*, ptrs::Environment>
gen_instruction_environment_map(const cfg::ControlFlowGraph& cfg,
const ptrs::FixpointIterator& fp_iter) {
std::unordered_map<const IRInstruction*, ptrs::Environment> result;
for (auto* block : cfg.blocks()) {
auto env = fp_iter.get_entry_state_at(block);
for (auto& mie : InstructionIterable(block)) {
auto* insn = mie.insn;
result.emplace(insn, env);
fp_iter.analyze_instruction(insn, &env);
}
}
return result;
}
std::string show(const cfg::ControlFlowGraph& cfg) {
const auto& blocks = cfg.blocks();
std::ostringstream ss;
ss << "CFG:\n";
for (const auto& b : blocks) {
ss << " Block B" << b->id() << ":\n";
ss << " preds:";
for (const auto& p : b->preds()) {
ss << " (" << *p << " B" << p->src()->id() << ")";
}
ss << "\n";
ss << show(b);
ss << " succs:";
for (auto& s : b->succs()) {
ss << " (" << *s << " B" << s->target()->id() << ")";
}
ss << "\n";
}
return ss.str();
}