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src/share/vm/opto/loopUnswitch.cpp@98cb887364d3 (annotated)

src/share/vm/opto/loopUnswitch.cpp

Fri, 27 Feb 2009 13:27:09 -0800

author

twisti

date

Fri, 27 Feb 2009 13:27:09 -0800

changeset 1040

98cb887364d3

parent 670

9c2ecc2ffb12

child 1907

c18cbe5936b8

permissions

-rw-r--r--

6810672: Comment typos
Summary: I have collected some typos I have found while looking at the code.
Reviewed-by: kvn, never

duke@435	1	/*
xdono@631	2	* Copyright 2006-2008 Sun Microsystems, Inc. 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	*
duke@435	19	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435	20	* CA 95054 USA or visit www.sun.com if you need additional information or
duke@435	21	* have any questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	#include "incls/_precompiled.incl"
duke@435	26	#include "incls/_loopUnswitch.cpp.incl"
duke@435	27
duke@435	28	//================= Loop Unswitching =====================
duke@435	29	//
duke@435	30	// orig: transformed:
duke@435	31	// if (invariant-test) then
duke@435	32	// loop loop
duke@435	33	// stmt1 stmt1
duke@435	34	// if (invariant-test) then stmt2
duke@435	35	// stmt2 stmt4
duke@435	36	// else endloop
duke@435	37	// stmt3 else
duke@435	38	// endif loop [clone]
duke@435	39	// stmt4 stmt1 [clone]
duke@435	40	// endloop stmt3
duke@435	41	// stmt4 [clone]
duke@435	42	// endloop
duke@435	43	// endif
duke@435	44	//
duke@435	45	// Note: the "else" clause may be empty
duke@435	46
duke@435	47	//------------------------------policy_unswitching-----------------------------
duke@435	48	// Return TRUE or FALSE if the loop should be unswitched
duke@435	49	// (ie. clone loop with an invariant test that does not exit the loop)
duke@435	50	bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
duke@435	51	if( !LoopUnswitching ) {
duke@435	52	return false;
duke@435	53	}
rasbold@543	54	if (!_head->is_Loop()) {
rasbold@543	55	return false;
rasbold@543	56	}
duke@435	57	uint nodes_left = MaxNodeLimit - phase->C->unique();
duke@435	58	if (2 * _body.size() > nodes_left) {
duke@435	59	return false; // Too speculative if running low on nodes.
duke@435	60	}
duke@435	61	LoopNode* head = _head->as_Loop();
duke@435	62	if (head->unswitch_count() + 1 > head->unswitch_max()) {
duke@435	63	return false;
duke@435	64	}
duke@435	65	return phase->find_unswitching_candidate(this) != NULL;
duke@435	66	}
duke@435	67
duke@435	68	//------------------------------find_unswitching_candidate-----------------------------
duke@435	69	// Find candidate "if" for unswitching
duke@435	70	IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {
duke@435	71
duke@435	72	// Find first invariant test that doesn't exit the loop
duke@435	73	LoopNode *head = loop->_head->as_Loop();
duke@435	74	IfNode* unswitch_iff = NULL;
duke@435	75	Node* n = head->in(LoopNode::LoopBackControl);
duke@435	76	while (n != head) {
duke@435	77	Node* n_dom = idom(n);
duke@435	78	if (n->is_Region()) {
duke@435	79	if (n_dom->is_If()) {
duke@435	80	IfNode* iff = n_dom->as_If();
duke@435	81	if (iff->in(1)->is_Bool()) {
duke@435	82	BoolNode* bol = iff->in(1)->as_Bool();
duke@435	83	if (bol->in(1)->is_Cmp()) {
duke@435	84	// If condition is invariant and not a loop exit,
duke@435	85	// then found reason to unswitch.
duke@435	86	if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {
duke@435	87	unswitch_iff = iff;
duke@435	88	}
duke@435	89	}
duke@435	90	}
duke@435	91	}
duke@435	92	}
duke@435	93	n = n_dom;
duke@435	94	}
duke@435	95	return unswitch_iff;
duke@435	96	}
duke@435	97
duke@435	98	//------------------------------do_unswitching-----------------------------
duke@435	99	// Clone loop with an invariant test (that does not exit) and
duke@435	100	// insert a clone of the test that selects which version to
duke@435	101	// execute.
duke@435	102	void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {
duke@435	103
duke@435	104	// Find first invariant test that doesn't exit the loop
duke@435	105	LoopNode *head = loop->_head->as_Loop();
duke@435	106
duke@435	107	IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
duke@435	108	assert(unswitch_iff != NULL, "should be at least one");
duke@435	109
duke@435	110	// Need to revert back to normal loop
duke@435	111	if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
duke@435	112	head->as_CountedLoop()->set_normal_loop();
duke@435	113	}
duke@435	114
duke@435	115	ProjNode* proj_true = create_slow_version_of_loop(loop, old_new);
duke@435	116
duke@435	117	assert(proj_true->is_IfTrue() && proj_true->unique_ctrl_out() == head, "by construction");
duke@435	118
duke@435	119	// Increment unswitch count
duke@435	120	LoopNode* head_clone = old_new[head->_idx]->as_Loop();
duke@435	121	int nct = head->unswitch_count() + 1;
duke@435	122	head->set_unswitch_count(nct);
duke@435	123	head_clone->set_unswitch_count(nct);
duke@435	124
duke@435	125	// Add test to new "if" outside of loop
duke@435	126	IfNode* invar_iff = proj_true->in(0)->as_If();
duke@435	127	Node* invar_iff_c = invar_iff->in(0);
duke@435	128	BoolNode* bol = unswitch_iff->in(1)->as_Bool();
duke@435	129	invar_iff->set_req(1, bol);
duke@435	130	invar_iff->_prob = unswitch_iff->_prob;
duke@435	131
duke@435	132	ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
duke@435	133
twisti@1040	134	// Hoist invariant casts out of each loop to the appropriate
duke@435	135	// control projection.
duke@435	136
duke@435	137	Node_List worklist;
duke@435	138
duke@435	139	for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
duke@435	140	ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
duke@435	141	// Copy to a worklist for easier manipulation
duke@435	142	for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
duke@435	143	Node* use = proj->fast_out(j);
duke@435	144	if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
duke@435	145	worklist.push(use);
duke@435	146	}
duke@435	147	}
duke@435	148	ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
duke@435	149	while (worklist.size() > 0) {
duke@435	150	Node* use = worklist.pop();
duke@435	151	Node* nuse = use->clone();
duke@435	152	nuse->set_req(0, invar_proj);
duke@435	153	_igvn.hash_delete(use);
duke@435	154	use->set_req(1, nuse);
duke@435	155	_igvn._worklist.push(use);
duke@435	156	register_new_node(nuse, invar_proj);
duke@435	157	// Same for the clone
duke@435	158	Node* use_clone = old_new[use->_idx];
duke@435	159	_igvn.hash_delete(use_clone);
duke@435	160	use_clone->set_req(1, nuse);
duke@435	161	_igvn._worklist.push(use_clone);
duke@435	162	}
duke@435	163	}
duke@435	164
duke@435	165	// Hardwire the control paths in the loops into if(true) and if(false)
duke@435	166	_igvn.hash_delete(unswitch_iff);
duke@435	167	short_circuit_if(unswitch_iff, proj_true);
duke@435	168	_igvn._worklist.push(unswitch_iff);
duke@435	169
duke@435	170	IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
duke@435	171	_igvn.hash_delete(unswitch_iff_clone);
duke@435	172	short_circuit_if(unswitch_iff_clone, proj_false);
duke@435	173	_igvn._worklist.push(unswitch_iff_clone);
duke@435	174
duke@435	175	// Reoptimize loops
duke@435	176	loop->record_for_igvn();
duke@435	177	for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
duke@435	178	Node *n = loop->_body[i];
duke@435	179	Node *n_clone = old_new[n->_idx];
duke@435	180	_igvn._worklist.push(n_clone);
duke@435	181	}
duke@435	182
duke@435	183	#ifndef PRODUCT
duke@435	184	if (TraceLoopUnswitching) {
duke@435	185	tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d",
duke@435	186	head->_idx, unswitch_iff->_idx,
duke@435	187	old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
duke@435	188	}
duke@435	189	#endif
duke@435	190
duke@435	191	C->set_major_progress();
duke@435	192	}
duke@435	193
duke@435	194	//-------------------------create_slow_version_of_loop------------------------
duke@435	195	// Create a slow version of the loop by cloning the loop
duke@435	196	// and inserting an if to select fast-slow versions.
duke@435	197	// Return control projection of the entry to the fast version.
duke@435	198	ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,
duke@435	199	Node_List &old_new) {
duke@435	200	LoopNode* head = loop->_head->as_Loop();
duke@435	201	Node* entry = head->in(LoopNode::EntryControl);
duke@435	202	_igvn.hash_delete(entry);
duke@435	203	_igvn._worklist.push(entry);
duke@435	204	IdealLoopTree* outer_loop = loop->_parent;
duke@435	205
duke@435	206	Node *cont = _igvn.intcon(1);
duke@435	207	set_ctrl(cont, C->root());
kvn@651	208	Node* opq = new (C, 2) Opaque1Node(C, cont);
duke@435	209	register_node(opq, outer_loop, entry, dom_depth(entry));
duke@435	210	Node *bol = new (C, 2) Conv2BNode(opq);
duke@435	211	register_node(bol, outer_loop, entry, dom_depth(entry));
duke@435	212	IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);
duke@435	213	register_node(iff, outer_loop, entry, dom_depth(entry));
duke@435	214	ProjNode* iffast = new (C, 1) IfTrueNode(iff);
duke@435	215	register_node(iffast, outer_loop, iff, dom_depth(iff));
duke@435	216	ProjNode* ifslow = new (C, 1) IfFalseNode(iff);
duke@435	217	register_node(ifslow, outer_loop, iff, dom_depth(iff));
duke@435	218
duke@435	219	// Clone the loop body. The clone becomes the fast loop. The
duke@435	220	// original pre-header will (illegally) have 2 control users (old & new loops).
duke@435	221	clone_loop(loop, old_new, dom_depth(head), iff);
duke@435	222	assert(old_new[head->_idx]->is_Loop(), "" );
duke@435	223
duke@435	224	// Fast (true) control
duke@435	225	_igvn.hash_delete(head);
duke@435	226	head->set_req(LoopNode::EntryControl, iffast);
duke@435	227	set_idom(head, iffast, dom_depth(head));
duke@435	228	_igvn._worklist.push(head);
duke@435	229
duke@435	230	// Slow (false) control
duke@435	231	LoopNode* slow_head = old_new[head->_idx]->as_Loop();
duke@435	232	_igvn.hash_delete(slow_head);
duke@435	233	slow_head->set_req(LoopNode::EntryControl, ifslow);
duke@435	234	set_idom(slow_head, ifslow, dom_depth(slow_head));
duke@435	235	_igvn._worklist.push(slow_head);
duke@435	236
duke@435	237	recompute_dom_depth();
duke@435	238
duke@435	239	return iffast;
duke@435	240	}