void BCEscapeAnalyzer::merge_block_states(StateInfo *blockstates, ciBlock *dest, StateInfo *s_state) {
StateInfo *d_state = blockstates+dest->index();
int nlocals = _method->max_locals();
// exceptions may cause transfer of control to handlers in the middle of a
// block, so we don't merge the incoming state of exception handlers
if (dest->is_handler())
return;
if (!d_state->_initialized ) {
// destination not initialized, just copy
for (int i = 0; i < nlocals; i++) {
d_state->_vars[i] = s_state->_vars[i];
}
for (int i = 0; i < s_state->_stack_height; i++) {
d_state->_stack[i] = s_state->_stack[i];
}
d_state->_stack_height = s_state->_stack_height;
d_state->_max_stack = s_state->_max_stack;
d_state->_initialized = true;
} else if (!dest->processed()) {
// we have not yet walked the bytecodes of dest, we can merge
// the states
assert(d_state->_stack_height == s_state->_stack_height, "computed stack heights must match");
for (int i = 0; i < nlocals; i++) {
d_state->_vars[i].set_union(s_state->_vars[i]);
}
for (int i = 0; i < s_state->_stack_height; i++) {
d_state->_stack[i].set_union(s_state->_stack[i]);
}
} else {
// the bytecodes of dest have already been processed, mark any
// arguments in the source state which are not in the dest state
// as global escape.
// Future refinement: we only need to mark these variable to the
// maximum escape of any variables in dest state
assert(d_state->_stack_height == s_state->_stack_height, "computed stack heights must match");
ArgumentMap extra_vars;
for (int i = 0; i < nlocals; i++) {
ArgumentMap t;
t = s_state->_vars[i];
t.set_difference(d_state->_vars[i]);
extra_vars.set_union(t);
}
for (int i = 0; i < s_state->_stack_height; i++) {
ArgumentMap t;
t.clear();
t = s_state->_stack[i];
t.set_difference(d_state->_stack[i]);
extra_vars.set_union(t);
}
set_global_escape(extra_vars);
}
}
StateInfo() {
empty_map.clear();
}
