diff -r fd16c54261b3 -r 489c9b5090e2 hotspot/src/share/vm/opto/loopUnswitch.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/hotspot/src/share/vm/opto/loopUnswitch.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,237 @@ +/* + * Copyright 2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +#include "incls/_precompiled.incl" +#include "incls/_loopUnswitch.cpp.incl" + +//================= 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; + } + 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"); + + // 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 appropiate + // 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(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; +}