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src/share/vm/opto/loopUnswitch.cpp@69ea58782b1a (annotated)

src/share/vm/opto/loopUnswitch.cpp

Thu, 31 Jul 2014 19:59:36 +0200

author

roland

date

Thu, 31 Jul 2014 19:59:36 +0200

changeset 7003

69ea58782b1a

parent 4315

2aff40cb4703

child 6876

710a3c8b516e

child 7385

9e69e8d1c900

permissions

-rw-r--r--

8054054: 8040121 is broken
Summary: C++ code pattern from 8040121 is incorrect
Reviewed-by: kvn

duke@435	1	/*
mikael@4153	2	* Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
trims@1907	19	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907	20	* or visit www.oracle.com if you need additional information or have any
trims@1907	21	* questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
stefank@2314	25	#include "precompiled.hpp"
stefank@2314	26	#include "memory/allocation.inline.hpp"
stefank@2314	27	#include "opto/connode.hpp"
stefank@2314	28	#include "opto/loopnode.hpp"
stefank@2314	29	#include "opto/rootnode.hpp"
duke@435	30
duke@435	31	//================= Loop Unswitching =====================
duke@435	32	//
duke@435	33	// orig: transformed:
duke@435	34	// if (invariant-test) then
kvn@2727	35	// predicate predicate
duke@435	36	// loop loop
duke@435	37	// stmt1 stmt1
duke@435	38	// if (invariant-test) then stmt2
duke@435	39	// stmt2 stmt4
duke@435	40	// else endloop
duke@435	41	// stmt3 else
kvn@2727	42	// endif predicate [clone]
kvn@2727	43	// stmt4 loop [clone]
kvn@2727	44	// endloop stmt1 [clone]
kvn@2727	45	// stmt3
duke@435	46	// stmt4 [clone]
duke@435	47	// endloop
duke@435	48	// endif
duke@435	49	//
duke@435	50	// Note: the "else" clause may be empty
duke@435	51
duke@435	52	//------------------------------policy_unswitching-----------------------------
duke@435	53	// Return TRUE or FALSE if the loop should be unswitched
duke@435	54	// (ie. clone loop with an invariant test that does not exit the loop)
duke@435	55	bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
duke@435	56	if( !LoopUnswitching ) {
duke@435	57	return false;
duke@435	58	}
rasbold@543	59	if (!_head->is_Loop()) {
rasbold@543	60	return false;
rasbold@543	61	}
bharadwaj@4315	62	uint nodes_left = MaxNodeLimit - phase->C->live_nodes();
duke@435	63	if (2 * _body.size() > nodes_left) {
duke@435	64	return false; // Too speculative if running low on nodes.
duke@435	65	}
duke@435	66	LoopNode* head = _head->as_Loop();
duke@435	67	if (head->unswitch_count() + 1 > head->unswitch_max()) {
duke@435	68	return false;
duke@435	69	}
duke@435	70	return phase->find_unswitching_candidate(this) != NULL;
duke@435	71	}
duke@435	72
duke@435	73	//------------------------------find_unswitching_candidate-----------------------------
duke@435	74	// Find candidate "if" for unswitching
duke@435	75	IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {
duke@435	76
duke@435	77	// Find first invariant test that doesn't exit the loop
duke@435	78	LoopNode *head = loop->_head->as_Loop();
duke@435	79	IfNode* unswitch_iff = NULL;
duke@435	80	Node* n = head->in(LoopNode::LoopBackControl);
duke@435	81	while (n != head) {
duke@435	82	Node* n_dom = idom(n);
duke@435	83	if (n->is_Region()) {
duke@435	84	if (n_dom->is_If()) {
duke@435	85	IfNode* iff = n_dom->as_If();
duke@435	86	if (iff->in(1)->is_Bool()) {
duke@435	87	BoolNode* bol = iff->in(1)->as_Bool();
duke@435	88	if (bol->in(1)->is_Cmp()) {
duke@435	89	// If condition is invariant and not a loop exit,
duke@435	90	// then found reason to unswitch.
duke@435	91	if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {
duke@435	92	unswitch_iff = iff;
duke@435	93	}
duke@435	94	}
duke@435	95	}
duke@435	96	}
duke@435	97	}
duke@435	98	n = n_dom;
duke@435	99	}
duke@435	100	return unswitch_iff;
duke@435	101	}
duke@435	102
duke@435	103	//------------------------------do_unswitching-----------------------------
duke@435	104	// Clone loop with an invariant test (that does not exit) and
duke@435	105	// insert a clone of the test that selects which version to
duke@435	106	// execute.
duke@435	107	void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {
duke@435	108
duke@435	109	// Find first invariant test that doesn't exit the loop
duke@435	110	LoopNode *head = loop->_head->as_Loop();
duke@435	111
duke@435	112	IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
duke@435	113	assert(unswitch_iff != NULL, "should be at least one");
duke@435	114
kvn@2665	115	#ifndef PRODUCT
kvn@2665	116	if (TraceLoopOpts) {
kvn@2665	117	tty->print("Unswitch %d ", head->unswitch_count()+1);
kvn@2665	118	loop->dump_head();
kvn@2665	119	}
kvn@2665	120	#endif
kvn@2665	121
duke@435	122	// Need to revert back to normal loop
duke@435	123	if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
duke@435	124	head->as_CountedLoop()->set_normal_loop();
duke@435	125	}
duke@435	126
duke@435	127	ProjNode* proj_true = create_slow_version_of_loop(loop, old_new);
duke@435	128
kvn@2727	129	#ifdef ASSERT
kvn@2727	130	Node* uniqc = proj_true->unique_ctrl_out();
kvn@2727	131	Node* entry = head->in(LoopNode::EntryControl);
kvn@2727	132	Node* predicate = find_predicate(entry);
kvn@2877	133	if (predicate != NULL && LoopLimitCheck && UseLoopPredicate) {
kvn@2877	134	// We may have two predicates, find first.
kvn@2877	135	entry = find_predicate(entry->in(0)->in(0));
kvn@2877	136	if (entry != NULL) predicate = entry;
kvn@2877	137	}
kvn@2727	138	if (predicate != NULL) predicate = predicate->in(0);
kvn@2727	139	assert(proj_true->is_IfTrue() &&
kvn@2727	140	(predicate == NULL && uniqc == head ||
kvn@2727	141	predicate != NULL && uniqc == predicate), "by construction");
kvn@2727	142	#endif
duke@435	143	// Increment unswitch count
duke@435	144	LoopNode* head_clone = old_new[head->_idx]->as_Loop();
duke@435	145	int nct = head->unswitch_count() + 1;
duke@435	146	head->set_unswitch_count(nct);
duke@435	147	head_clone->set_unswitch_count(nct);
duke@435	148
duke@435	149	// Add test to new "if" outside of loop
duke@435	150	IfNode* invar_iff = proj_true->in(0)->as_If();
duke@435	151	Node* invar_iff_c = invar_iff->in(0);
duke@435	152	BoolNode* bol = unswitch_iff->in(1)->as_Bool();
duke@435	153	invar_iff->set_req(1, bol);
duke@435	154	invar_iff->_prob = unswitch_iff->_prob;
duke@435	155
duke@435	156	ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
duke@435	157
twisti@1040	158	// Hoist invariant casts out of each loop to the appropriate
duke@435	159	// control projection.
duke@435	160
duke@435	161	Node_List worklist;
duke@435	162
duke@435	163	for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
duke@435	164	ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
duke@435	165	// Copy to a worklist for easier manipulation
duke@435	166	for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
duke@435	167	Node* use = proj->fast_out(j);
duke@435	168	if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
duke@435	169	worklist.push(use);
duke@435	170	}
duke@435	171	}
duke@435	172	ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
duke@435	173	while (worklist.size() > 0) {
duke@435	174	Node* use = worklist.pop();
duke@435	175	Node* nuse = use->clone();
duke@435	176	nuse->set_req(0, invar_proj);
kvn@3847	177	_igvn.replace_input_of(use, 1, nuse);
duke@435	178	register_new_node(nuse, invar_proj);
duke@435	179	// Same for the clone
duke@435	180	Node* use_clone = old_new[use->_idx];
kvn@3847	181	_igvn.replace_input_of(use_clone, 1, nuse);
duke@435	182	}
duke@435	183	}
duke@435	184
duke@435	185	// Hardwire the control paths in the loops into if(true) and if(false)
kvn@3847	186	_igvn.rehash_node_delayed(unswitch_iff);
duke@435	187	short_circuit_if(unswitch_iff, proj_true);
duke@435	188
duke@435	189	IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
kvn@3847	190	_igvn.rehash_node_delayed(unswitch_iff_clone);
duke@435	191	short_circuit_if(unswitch_iff_clone, proj_false);
duke@435	192
duke@435	193	// Reoptimize loops
duke@435	194	loop->record_for_igvn();
duke@435	195	for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
duke@435	196	Node *n = loop->_body[i];
duke@435	197	Node *n_clone = old_new[n->_idx];
duke@435	198	_igvn._worklist.push(n_clone);
duke@435	199	}
duke@435	200
duke@435	201	#ifndef PRODUCT
duke@435	202	if (TraceLoopUnswitching) {
duke@435	203	tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d",
duke@435	204	head->_idx, unswitch_iff->_idx,
duke@435	205	old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
duke@435	206	}
duke@435	207	#endif
duke@435	208
duke@435	209	C->set_major_progress();
duke@435	210	}
duke@435	211
duke@435	212	//-------------------------create_slow_version_of_loop------------------------
duke@435	213	// Create a slow version of the loop by cloning the loop
duke@435	214	// and inserting an if to select fast-slow versions.
duke@435	215	// Return control projection of the entry to the fast version.
duke@435	216	ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,
duke@435	217	Node_List &old_new) {
duke@435	218	LoopNode* head = loop->_head->as_Loop();
kvn@2877	219	bool counted_loop = head->is_CountedLoop();
duke@435	220	Node* entry = head->in(LoopNode::EntryControl);
kvn@3847	221	_igvn.rehash_node_delayed(entry);
duke@435	222	IdealLoopTree* outer_loop = loop->_parent;
duke@435	223
duke@435	224	Node *cont = _igvn.intcon(1);
duke@435	225	set_ctrl(cont, C->root());
kvn@4115	226	Node* opq = new (C) Opaque1Node(C, cont);
duke@435	227	register_node(opq, outer_loop, entry, dom_depth(entry));
kvn@4115	228	Node *bol = new (C) Conv2BNode(opq);
duke@435	229	register_node(bol, outer_loop, entry, dom_depth(entry));
kvn@4115	230	IfNode* iff = new (C) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);
duke@435	231	register_node(iff, outer_loop, entry, dom_depth(entry));
kvn@4115	232	ProjNode* iffast = new (C) IfTrueNode(iff);
duke@435	233	register_node(iffast, outer_loop, iff, dom_depth(iff));
kvn@4115	234	ProjNode* ifslow = new (C) IfFalseNode(iff);
duke@435	235	register_node(ifslow, outer_loop, iff, dom_depth(iff));
duke@435	236
duke@435	237	// Clone the loop body. The clone becomes the fast loop. The
kvn@2727	238	// original pre-header will (illegally) have 3 control users
kvn@2727	239	// (old & new loops & new if).
duke@435	240	clone_loop(loop, old_new, dom_depth(head), iff);
duke@435	241	assert(old_new[head->_idx]->is_Loop(), "" );
duke@435	242
duke@435	243	// Fast (true) control
kvn@2877	244	Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop);
kvn@3847	245	_igvn.replace_input_of(head, LoopNode::EntryControl, iffast_pred);
kvn@2727	246	set_idom(head, iffast_pred, dom_depth(head));
duke@435	247
duke@435	248	// Slow (false) control
kvn@3043	249	Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop);
duke@435	250	LoopNode* slow_head = old_new[head->_idx]->as_Loop();
kvn@3847	251	_igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow_pred);
kvn@2727	252	set_idom(slow_head, ifslow_pred, dom_depth(slow_head));
duke@435	253
duke@435	254	recompute_dom_depth();
duke@435	255
duke@435	256	return iffast;
duke@435	257	}