//------------------------------policy_unswitching-----------------------------
// Return TRUE or FALSE if the loop should be unswitched
// (ie. clone loop with an invariant test that does not exit the loop)
bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
if( !LoopUnswitching ) {
return false;
}
uint nodes_left = MaxNodeLimit - phase->C->unique();
if (2 * _body.size() > nodes_left) {
return false; // Too speculative if running low on nodes.
}
LoopNode* head = _head->as_Loop();
if (head->unswitch_count() + 1 > head->unswitch_max()) {
return false;
}
return phase->find_unswitching_candidate(this) != NULL;
}
//------------------------------policy_unswitching-----------------------------
// Return TRUE or FALSE if the loop should be unswitched
// (ie. clone loop with an invariant test that does not exit the loop)
bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
if( !LoopUnswitching ) {
return false;
}
if (!_head->is_Loop()) {
return false;
}
// check for vectorized loops, any unswitching was already applied
if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) {
return false;
}
int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes();
if ((int)(2 * _body.size()) > nodes_left) {
return false; // Too speculative if running low on nodes.
}
LoopNode* head = _head->as_Loop();
if (head->unswitch_count() + 1 > head->unswitch_max()) {
return false;
}
return phase->find_unswitching_candidate(this) != NULL;
}
//------------------------------do_unswitching-----------------------------
// Clone loop with an invariant test (that does not exit) and
// insert a clone of the test that selects which version to
// execute.
void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {
// Find first invariant test that doesn't exit the loop
LoopNode *head = loop->_head->as_Loop();
IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
assert(unswitch_iff != NULL, "should be at least one");
// Need to revert back to normal loop
if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
head->as_CountedLoop()->set_normal_loop();
}
ProjNode* proj_true = create_slow_version_of_loop(loop, old_new);
assert(proj_true->is_IfTrue() && proj_true->unique_ctrl_out() == head, "by construction");
// Increment unswitch count
LoopNode* head_clone = old_new[head->_idx]->as_Loop();
int nct = head->unswitch_count() + 1;
head->set_unswitch_count(nct);
head_clone->set_unswitch_count(nct);
// Add test to new "if" outside of loop
IfNode* invar_iff = proj_true->in(0)->as_If();
Node* invar_iff_c = invar_iff->in(0);
BoolNode* bol = unswitch_iff->in(1)->as_Bool();
invar_iff->set_req(1, bol);
invar_iff->_prob = unswitch_iff->_prob;
ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
// Hoist invariant casts out of each loop to the appropriate
// control projection.
Node_List worklist;
for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
// Copy to a worklist for easier manipulation
for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
Node* use = proj->fast_out(j);
if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
worklist.push(use);
}
}
ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
while (worklist.size() > 0) {
Node* use = worklist.pop();
Node* nuse = use->clone();
nuse->set_req(0, invar_proj);
_igvn.hash_delete(use);
use->set_req(1, nuse);
_igvn._worklist.push(use);
register_new_node(nuse, invar_proj);
// Same for the clone
Node* use_clone = old_new[use->_idx];
_igvn.hash_delete(use_clone);
use_clone->set_req(1, nuse);
_igvn._worklist.push(use_clone);
}
}
// Hardwire the control paths in the loops into if(true) and if(false)
_igvn.hash_delete(unswitch_iff);
short_circuit_if(unswitch_iff, proj_true);
_igvn._worklist.push(unswitch_iff);
IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
_igvn.hash_delete(unswitch_iff_clone);
short_circuit_if(unswitch_iff_clone, proj_false);
_igvn._worklist.push(unswitch_iff_clone);
// Reoptimize loops
loop->record_for_igvn();
for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
Node *n = loop->_body[i];
Node *n_clone = old_new[n->_idx];
_igvn._worklist.push(n_clone);
}
#ifndef PRODUCT
if (TraceLoopUnswitching) {
tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d",
head->_idx, unswitch_iff->_idx,
old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
}
#endif
C->set_major_progress();
}
