loopTransform.cpp (2230:9dc311b8473e) loopTransform.cpp (2250:1927db75dd85)
1/*
2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *

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1603
1604 if (!_head->is_CountedLoop())
1605 return false; // Dead loop
1606 CountedLoopNode *cl = _head->as_CountedLoop();
1607 if (!cl->loopexit())
1608 return false; // Malformed loop
1609 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
1610 return false; // Infinite loop
1/*
2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *

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1603
1604 if (!_head->is_CountedLoop())
1605 return false; // Dead loop
1606 CountedLoopNode *cl = _head->as_CountedLoop();
1607 if (!cl->loopexit())
1608 return false; // Malformed loop
1609 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
1610 return false; // Infinite loop
1611#ifndef PRODUCT
1612 if (PrintOpto) {
1613 tty->print("Removing empty loop");
1614 this->dump_head();
1615 } else if (TraceLoopOpts) {
1616 tty->print("Empty ");
1617 this->dump_head();
1618 }
1619#endif
1611
1620#ifdef ASSERT
1621 // Ensure only one phi which is the iv.
1622 Node* iv = NULL;
1623 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
1624 Node* n = cl->fast_out(i);
1625 if (n->Opcode() == Op_Phi) {
1626 assert(iv == NULL, "Too many phis" );
1627 iv = n;
1628 }
1629 }
1630 assert(iv == cl->phi(), "Wrong phi" );
1631#endif
1612#ifdef ASSERT
1613 // Ensure only one phi which is the iv.
1614 Node* iv = NULL;
1615 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
1616 Node* n = cl->fast_out(i);
1617 if (n->Opcode() == Op_Phi) {
1618 assert(iv == NULL, "Too many phis" );
1619 iv = n;
1620 }
1621 }
1622 assert(iv == cl->phi(), "Wrong phi" );
1623#endif
1624
1625 // main and post loops have explicitly created zero trip guard
1626 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
1627 if (needs_guard) {
1628 // Check for an obvious zero trip guard.
1629 Node* inctrl = cl->in(LoopNode::EntryControl);
1630 if (inctrl->Opcode() == Op_IfTrue) {
1631 // The test should look like just the backedge of a CountedLoop
1632 Node* iff = inctrl->in(0);
1633 if (iff->is_If()) {
1634 Node* bol = iff->in(1);
1635 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
1636 Node* cmp = bol->in(1);
1637 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
1638 needs_guard = false;
1639 }
1640 }
1641 }
1642 }
1643 }
1644
1645#ifndef PRODUCT
1646 if (PrintOpto) {
1647 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
1648 this->dump_head();
1649 } else if (TraceLoopOpts) {
1650 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
1651 this->dump_head();
1652 }
1653#endif
1654
1655 if (needs_guard) {
1656 // Peel the loop to ensure there's a zero trip guard
1657 Node_List old_new;
1658 phase->do_peeling(this, old_new);
1659 }
1660
1632 // Replace the phi at loop head with the final value of the last
1633 // iteration. Then the CountedLoopEnd will collapse (backedge never
1634 // taken) and all loop-invariant uses of the exit values will be correct.
1635 Node *phi = cl->phi();
1636 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
1637 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
1638 phase->_igvn.replace_node(phi,final);
1639 phase->C->set_major_progress();

--- 1178 unchanged lines hidden --- 		1661 // Replace the phi at loop head with the final value of the last
1662 // iteration. Then the CountedLoopEnd will collapse (backedge never
1663 // taken) and all loop-invariant uses of the exit values will be correct.
1664 Node *phi = cl->phi();
1665 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
1666 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
1667 phase->_igvn.replace_node(phi,final);
1668 phase->C->set_major_progress();

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