1 /*
2 * Copyright (c) 1997, 2013, 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 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/addnode.hpp"
28 #include "opto/compile.hpp"
29 #include "opto/constnode.hpp"
30 #include "opto/machnode.hpp"
31 #include "opto/matcher.hpp"
32 #include "opto/memnode.hpp"
33 #include "opto/phaseX.hpp"
34 #include "opto/subnode.hpp"
35 #include "runtime/sharedRuntime.hpp"
36
37 // Optimization - Graph Style
38
39 //=============================================================================
40 //------------------------------hash-------------------------------------------
41 uint ConNode::hash() const {
42 return (uintptr_t)in(TypeFunc::Control) + _type->hash();
43 }
44
45 //------------------------------make-------------------------------------------
46 ConNode *ConNode::make( Compile* C, const Type *t ) {
47 switch( t->basic_type() ) {
48 case T_INT: return new (C) ConINode( t->is_int() );
49 case T_LONG: return new (C) ConLNode( t->is_long() );
50 case T_FLOAT: return new (C) ConFNode( t->is_float_constant() );
51 case T_DOUBLE: return new (C) ConDNode( t->is_double_constant() );
52 case T_VOID: return new (C) ConNode ( Type::TOP );
53 case T_OBJECT: return new (C) ConPNode( t->is_ptr() );
54 case T_ARRAY: return new (C) ConPNode( t->is_aryptr() );
55 case T_ADDRESS: return new (C) ConPNode( t->is_ptr() );
56 case T_NARROWOOP: return new (C) ConNNode( t->is_narrowoop() );
57 case T_NARROWKLASS: return new (C) ConNKlassNode( t->is_narrowklass() );
58 case T_METADATA: return new (C) ConPNode( t->is_ptr() );
59 // Expected cases: TypePtr::NULL_PTR, any is_rawptr()
60 // Also seen: AnyPtr(TopPTR *+top); from command line:
61 // r -XX:+PrintOpto -XX:CIStart=285 -XX:+CompileTheWorld -XX:CompileTheWorldStartAt=660
62 // %%%% Stop using TypePtr::NULL_PTR to represent nulls: use either TypeRawPtr::NULL_PTR
63 // or else TypeOopPtr::NULL_PTR. Then set Type::_basic_type[AnyPtr] = T_ILLEGAL
64 }
65 ShouldNotReachHere();
66 return NULL;
67 }
68
69 //=============================================================================
70 /*
71 The major change is for CMoveP and StrComp. They have related but slightly
72 different problems. They both take in TWO oops which are both null-checked
73 independently before the using Node. After CCP removes the CastPP's they need
74 to pick up the guarding test edge - in this case TWO control edges. I tried
75 various solutions, all have problems:
76
77 (1) Do nothing. This leads to a bug where we hoist a Load from a CMoveP or a
78 StrComp above a guarding null check. I've seen both cases in normal -Xcomp
79 testing.
80
81 (2) Plug the control edge from 1 of the 2 oops in. Apparent problem here is
82 to figure out which test post-dominates. The real problem is that it doesn't
83 matter which one you pick. After you pick up, the dominating-test elider in
84 IGVN can remove the test and allow you to hoist up to the dominating test on
85 the chosen oop bypassing the test on the not-chosen oop. Seen in testing.
86 Oops.
87
88 (3) Leave the CastPP's in. This makes the graph more accurate in some sense;
89 we get to keep around the knowledge that an oop is not-null after some test.
90 Alas, the CastPP's interfere with GVN (some values are the regular oop, some
91 are the CastPP of the oop, all merge at Phi's which cannot collapse, etc).
92 This cost us 10% on SpecJVM, even when I removed some of the more trivial
93 cases in the optimizer. Removing more useless Phi's started allowing Loads to
94 illegally float above null checks. I gave up on this approach.
95
96 (4) Add BOTH control edges to both tests. Alas, too much code knows that
97 control edges are in slot-zero ONLY. Many quick asserts fail; no way to do
98 this one. Note that I really want to allow the CMoveP to float and add both
99 control edges to the dependent Load op - meaning I can select early but I
100 cannot Load until I pass both tests.
101
102 (5) Do not hoist CMoveP and StrComp. To this end I added the v-call
103 depends_only_on_test(). No obvious performance loss on Spec, but we are
104 clearly conservative on CMoveP (also so on StrComp but that's unlikely to
105 matter ever).
106
107 */
108
109