/* * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "memory/allocation.inline.hpp" #include "opto/connode.hpp" #include "opto/loopnode.hpp" #include "opto/rootnode.hpp" //================= Loop Unswitching ===================== // // orig: transformed: // if (invariant-test) then // loop loop // stmt1 stmt1 // if (invariant-test) then stmt2 // stmt2 stmt4 // else endloop // stmt3 else // endif loop [clone] // stmt4 stmt1 [clone] // endloop stmt3 // stmt4 [clone] // endloop // endif // // Note: the "else" clause may be empty //------------------------------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; } 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; } //------------------------------find_unswitching_candidate----------------------------- // Find candidate "if" for unswitching IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const { // Find first invariant test that doesn't exit the loop LoopNode *head = loop->_head->as_Loop(); IfNode* unswitch_iff = NULL; Node* n = head->in(LoopNode::LoopBackControl); while (n != head) { Node* n_dom = idom(n); if (n->is_Region()) { if (n_dom->is_If()) { IfNode* iff = n_dom->as_If(); if (iff->in(1)->is_Bool()) { BoolNode* bol = iff->in(1)->as_Bool(); if (bol->in(1)->is_Cmp()) { // If condition is invariant and not a loop exit, // then found reason to unswitch. if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { unswitch_iff = iff; } } } } } n = n_dom; } return unswitch_iff; } //------------------------------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"); #ifndef PRODUCT if (TraceLoopOpts) { tty->print("Unswitch %d ", head->unswitch_count()+1); loop->dump_head(); } #endif // 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(); } //-------------------------create_slow_version_of_loop------------------------ // Create a slow version of the loop by cloning the loop // and inserting an if to select fast-slow versions. // Return control projection of the entry to the fast version. ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, Node_List &old_new) { LoopNode* head = loop->_head->as_Loop(); Node* entry = head->in(LoopNode::EntryControl); _igvn.hash_delete(entry); _igvn._worklist.push(entry); IdealLoopTree* outer_loop = loop->_parent; Node *cont = _igvn.intcon(1); set_ctrl(cont, C->root()); Node* opq = new (C, 2) Opaque1Node(C, cont); register_node(opq, outer_loop, entry, dom_depth(entry)); Node *bol = new (C, 2) Conv2BNode(opq); register_node(bol, outer_loop, entry, dom_depth(entry)); IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); register_node(iff, outer_loop, entry, dom_depth(entry)); ProjNode* iffast = new (C, 1) IfTrueNode(iff); register_node(iffast, outer_loop, iff, dom_depth(iff)); ProjNode* ifslow = new (C, 1) IfFalseNode(iff); register_node(ifslow, outer_loop, iff, dom_depth(iff)); // Clone the loop body. The clone becomes the fast loop. The // original pre-header will (illegally) have 2 control users (old & new loops). clone_loop(loop, old_new, dom_depth(head), iff); assert(old_new[head->_idx]->is_Loop(), "" ); // Fast (true) control _igvn.hash_delete(head); head->set_req(LoopNode::EntryControl, iffast); set_idom(head, iffast, dom_depth(head)); _igvn._worklist.push(head); // Slow (false) control LoopNode* slow_head = old_new[head->_idx]->as_Loop(); _igvn.hash_delete(slow_head); slow_head->set_req(LoopNode::EntryControl, ifslow); set_idom(slow_head, ifslow, dom_depth(slow_head)); _igvn._worklist.push(slow_head); recompute_dom_depth(); return iffast; }