1/*
2 * Copyright (C) 2017 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "B3HoistLoopInvariantValues.h"
28
29#if ENABLE(B3_JIT)
30
31#include "B3BackwardsDominators.h"
32#include "B3BasicBlockInlines.h"
33#include "B3Dominators.h"
34#include "B3EnsureLoopPreHeaders.h"
35#include "B3NaturalLoops.h"
36#include "B3PhaseScope.h"
37#include "B3ProcedureInlines.h"
38#include "B3ValueInlines.h"
39#include <wtf/RangeSet.h>
40
41namespace JSC { namespace B3 {
42
43bool hoistLoopInvariantValues(Procedure& proc)
44{
45 PhaseScope phaseScope(proc, "hoistLoopInvariantValues");
46
47 ensureLoopPreHeaders(proc);
48
49 NaturalLoops& loops = proc.naturalLoops();
50 if (!loops.numLoops())
51 return false;
52
53 proc.resetValueOwners();
54 Dominators& dominators = proc.dominators();
55 BackwardsDominators& backwardsDominators = proc.backwardsDominators();
56
57 // FIXME: We should have a reusable B3::EffectsSet data structure.
58 // https://bugs.webkit.org/show_bug.cgi?id=174762
59 struct LoopData {
60 RangeSet<HeapRange> writes;
61 bool writesLocalState { false };
62 bool writesPinned { false };
63 bool sideExits { false };
64 BasicBlock* preHeader { nullptr };
65 };
66
67 IndexMap<NaturalLoop, LoopData> data(loops.numLoops());
68
69 for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
70 const NaturalLoop& loop = loops.loop(loopIndex);
71 for (BasicBlock* predecessor : loop.header()->predecessors()) {
72 if (loops.belongsTo(predecessor, loop))
73 continue;
74 RELEASE_ASSERT(!data[loop].preHeader);
75 data[loop].preHeader = predecessor;
76 }
77 }
78
79 for (BasicBlock* block : proc) {
80 const NaturalLoop* loop = loops.innerMostLoopOf(block);
81 if (!loop)
82 continue;
83 for (Value* value : *block) {
84 Effects effects = value->effects();
85 data[*loop].writes.add(effects.writes);
86 data[*loop].writesLocalState |= effects.writesLocalState;
87 data[*loop].writesPinned |= effects.writesPinned;
88 data[*loop].sideExits |= effects.exitsSideways;
89 }
90 }
91
92 for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
93 const NaturalLoop& loop = loops.loop(loopIndex);
94 for (const NaturalLoop* current = loops.innerMostOuterLoop(loop); current; current = loops.innerMostOuterLoop(*current)) {
95 data[*current].writes.addAll(data[loop].writes);
96 data[*current].writesLocalState |= data[loop].writesLocalState;
97 data[*current].writesPinned |= data[loop].writesPinned;
98 data[*current].sideExits |= data[loop].sideExits;
99 }
100 }
101
102 bool changed = false;
103
104 // Pre-order ensures that we visit our dominators before we visit ourselves. Otherwise we'd miss some
105 // hoisting opportunities in complex CFGs.
106 for (BasicBlock* block : proc.blocksInPreOrder()) {
107 Vector<const NaturalLoop*> blockLoops = loops.loopsOf(block);
108 if (blockLoops.isEmpty())
109 continue;
110
111 for (Value*& value : *block) {
112 Effects effects = value->effects();
113
114 // We never hoist write effects or control constructs.
115 if (effects.mustExecute())
116 continue;
117
118 // Try outermost loop first.
119 for (unsigned i = blockLoops.size(); i--;) {
120 const NaturalLoop& loop = *blockLoops[i];
121
122 bool ok = true;
123 for (Value* child : value->children()) {
124 if (!dominators.dominates(child->owner, data[loop].preHeader)) {
125 ok = false;
126 break;
127 }
128 }
129 if (!ok)
130 continue;
131
132 if (effects.controlDependent) {
133 if (!backwardsDominators.dominates(block, data[loop].preHeader))
134 continue;
135
136 // FIXME: This is super conservative. In reality, we just need to make sure that there
137 // aren't any side exits between here and the pre-header according to backwards search.
138 // https://bugs.webkit.org/show_bug.cgi?id=174763
139 if (data[loop].sideExits)
140 continue;
141 }
142
143 if (effects.readsPinned && data[loop].writesPinned)
144 continue;
145
146 if (effects.readsLocalState && data[loop].writesLocalState)
147 continue;
148
149 if (data[loop].writes.overlaps(effects.reads))
150 continue;
151
152 data[loop].preHeader->appendNonTerminal(value);
153 value = proc.add<Value>(Nop, Void, value->origin());
154 changed = true;
155 }
156 }
157 }
158
159 return changed;
160}
161
162} } // namespace JSC::B3
163
164#endif // ENABLE(B3_JIT)
165
166