1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
|
/*
* Copyright 2019 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//
// Turn indirect calls into direct calls. This is possible if we know
// the table cannot change, and if we see a constant argument for the
// indirect call's index.
//
#include <unordered_map>
#include "call-utils.h"
#include "ir/table-utils.h"
#include "ir/type-updating.h"
#include "ir/utils.h"
#include "pass.h"
#include "wasm-builder.h"
#include "wasm-traversal.h"
#include "wasm.h"
namespace wasm {
namespace {
struct FunctionDirectizer : public WalkerPass<PostWalker<FunctionDirectizer>> {
bool isFunctionParallel() override { return true; }
Pass* create() override { return new FunctionDirectizer(tables); }
FunctionDirectizer(
const std::unordered_map<Name, TableUtils::FlatTable>& tables)
: tables(tables) {}
void visitCallIndirect(CallIndirect* curr) {
auto it = tables.find(curr->table);
if (it == tables.end()) {
return;
}
auto& flatTable = it->second;
// If the target is constant, we can emit a direct call.
if (curr->target->is<Const>()) {
std::vector<Expression*> operands(curr->operands.begin(),
curr->operands.end());
replaceCurrent(makeDirectCall(operands, curr->target, flatTable, curr));
return;
}
// Emit direct calls for things like a select over constants.
if (auto* calls = CallUtils::convertToDirectCalls(
curr,
[&](Expression* target) {
return getTargetInfo(target, flatTable, curr);
},
*getFunction(),
*getModule())) {
replaceCurrent(calls);
// Note that types may have changed, as the utility here can add locals
// which require fixups if they are non-nullable, for example.
changedTypes = true;
return;
}
}
void doWalkFunction(Function* func) {
WalkerPass<PostWalker<FunctionDirectizer>>::doWalkFunction(func);
if (changedTypes) {
ReFinalize().walkFunctionInModule(func, getModule());
TypeUpdating::handleNonDefaultableLocals(func, *getModule());
}
}
private:
const std::unordered_map<Name, TableUtils::FlatTable>& tables;
bool changedTypes = false;
// Given an expression that we will use as the target of an indirect call,
// analyze it and return one of the results of CallUtils::IndirectCallInfo,
// that is, whether we know a direct call target, or we know it will trap, or
// if we know nothing.
CallUtils::IndirectCallInfo
getTargetInfo(Expression* target,
const TableUtils::FlatTable& flatTable,
CallIndirect* original) {
auto* c = target->dynCast<Const>();
if (!c) {
return CallUtils::Unknown{};
}
Index index = c->value.geti32();
// If the index is invalid, or the type is wrong, then this will trap.
if (index >= flatTable.names.size()) {
return CallUtils::Trap{};
}
auto name = flatTable.names[index];
if (!name.is()) {
return CallUtils::Trap{};
}
auto* func = getModule()->getFunction(name);
if (original->heapType != func->type) {
return CallUtils::Trap{};
}
return CallUtils::Known{name};
}
// Create a direct call for a given list of operands, an expression which is
// known to contain a constant indicating the table offset, and the relevant
// table. If we can see that the call will trap, instead return an
// unreachable.
Expression* makeDirectCall(const std::vector<Expression*>& operands,
Expression* c,
const TableUtils::FlatTable& flatTable,
CallIndirect* original) {
// If the index is invalid, or the type is wrong, we can
// emit an unreachable here, since in Binaryen it is ok to
// reorder/replace traps when optimizing (but never to
// remove them, at least not by default).
auto info = getTargetInfo(c, flatTable, original);
if (std::get_if<CallUtils::Trap>(&info)) {
return replaceWithUnreachable(operands);
}
assert(std::get_if<CallUtils::Known>(&info));
auto name = std::get_if<CallUtils::Known>(&info)->target;
// Everything looks good!
return Builder(*getModule())
.makeCall(name, operands, original->type, original->isReturn);
}
Expression* replaceWithUnreachable(const std::vector<Expression*>& operands) {
// Emitting an unreachable means we must update parent types.
changedTypes = true;
Builder builder(*getModule());
std::vector<Expression*> newOperands;
for (auto* operand : operands) {
newOperands.push_back(builder.makeDrop(operand));
}
return builder.makeSequence(builder.makeBlock(newOperands),
builder.makeUnreachable());
}
};
struct Directize : public Pass {
void run(PassRunner* runner, Module* module) override {
// Find which tables are valid to optimize on. They must not be imported nor
// exported (so the outside cannot modify them), and must have no sets in
// any part of the module.
// First, find which tables have sets.
using TablesWithSet = std::unordered_set<Name>;
ModuleUtils::ParallelFunctionAnalysis<TablesWithSet> analysis(
*module, [&](Function* func, TablesWithSet& tablesWithSet) {
if (func->imported()) {
return;
}
for (auto* set : FindAll<TableSet>(func->body).list) {
tablesWithSet.insert(set->table);
}
});
TablesWithSet tablesWithSet;
for (auto& [_, names] : analysis.map) {
for (auto name : names) {
tablesWithSet.insert(name);
}
}
std::unordered_map<Name, TableUtils::FlatTable> validTables;
for (auto& table : module->tables) {
if (table->imported()) {
continue;
}
if (tablesWithSet.count(table->name)) {
continue;
}
bool canOptimizeCallIndirect = true;
for (auto& ex : module->exports) {
if (ex->kind == ExternalKind::Table && ex->value == table->name) {
canOptimizeCallIndirect = false;
break;
}
}
if (!canOptimizeCallIndirect) {
continue;
}
// All conditions are valid, this is optimizable.
TableUtils::FlatTable flatTable(*module, *table);
if (flatTable.valid) {
validTables.emplace(table->name, flatTable);
}
}
if (validTables.empty()) {
return;
}
FunctionDirectizer(validTables).run(runner, module);
}
};
} // anonymous namespace
Pass* createDirectizePass() { return new Directize(); }
} // namespace wasm
|
