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
228
229
230
231
232
233
234
235
236
237
238
239
240
|
/*
* Copyright 2015 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.
*/
//
// Misc optimizations that are useful for and/or are only valid for
// emscripten output.
//
#include <asmjs/shared-constants.h>
#include <ir/import-utils.h>
#include <ir/localize.h>
#include <ir/memory-utils.h>
#include <ir/module-utils.h>
#include <ir/table-utils.h>
#include <pass.h>
#include <shared-constants.h>
#include <wasm-builder.h>
#include <wasm-emscripten.h>
#include <wasm.h>
#define DEBUG_TYPE "post-emscripten"
namespace wasm {
namespace {
static bool isInvoke(Function* F) {
return F->imported() && F->module == ENV && F->base.startsWith("invoke_");
}
struct OptimizeCalls : public WalkerPass<PostWalker<OptimizeCalls>> {
bool isFunctionParallel() override { return true; }
Pass* create() override { return new OptimizeCalls; }
void visitCall(Call* curr) {
// special asm.js imports can be optimized
auto* func = getModule()->getFunction(curr->target);
if (!func->imported()) {
return;
}
if (func->module == GLOBAL_MATH) {
if (func->base == POW) {
if (auto* exponent = curr->operands[1]->dynCast<Const>()) {
if (exponent->value == Literal(double(2.0))) {
// This is just a square operation, do a multiply
Localizer localizer(curr->operands[0], getFunction(), getModule());
Builder builder(*getModule());
replaceCurrent(builder.makeBinary(
MulFloat64,
localizer.expr,
builder.makeLocalGet(localizer.index, localizer.expr->type)));
} else if (exponent->value == Literal(double(0.5))) {
// This is just a square root operation
replaceCurrent(
Builder(*getModule()).makeUnary(SqrtFloat64, curr->operands[0]));
}
}
}
}
}
};
} // namespace
struct PostEmscripten : public Pass {
void run(PassRunner* runner, Module* module) override {
// Apply the stack pointer, if it was provided. This is needed here
// because the emscripten JS compiler can add static data allocations that
// come before the stack.
auto stackPtrStr =
runner->options.getArgumentOrDefault("stack-pointer", "");
if (stackPtrStr != "") {
Global* stackPointer = getStackPointerGlobal(*module);
BYN_TRACE("stack_pointer: " << stackPtrStr << "\n");
if (stackPointer && !stackPointer->imported()) {
auto stackPtr = std::stoi(stackPtrStr);
auto oldValue = stackPointer->init->cast<Const>()->value;
BYN_TRACE("updating __stack_pointer: " << oldValue.geti32() << " -> "
<< stackPtr << "\n");
stackPointer->init = Builder(*module).makeConst(int32_t(stackPtr));
}
}
// Apply the sbrk ptr, if it was provided.
auto sbrkPtrStr =
runner->options.getArgumentOrDefault("emscripten-sbrk-ptr", "");
if (sbrkPtrStr != "") {
auto sbrkPtr = std::stoi(sbrkPtrStr);
ImportInfo imports(*module);
auto* func = imports.getImportedFunction(ENV, "emscripten_get_sbrk_ptr");
if (func) {
Builder builder(*module);
func->body = builder.makeConst(int32_t(sbrkPtr));
func->module = func->base = Name();
}
// Apply the sbrk ptr value, if it was provided. This lets emscripten set
// up sbrk entirely in wasm, without depending on the JS side to init
// anything; this is necessary for standalone wasm mode, in which we do
// not have any JS. Otherwise, the JS would set this value during
// startup.
auto sbrkValStr =
runner->options.getArgumentOrDefault("emscripten-sbrk-val", "");
if (sbrkValStr != "") {
uint32_t sbrkVal = std::stoi(sbrkValStr);
auto end = sbrkPtr + sizeof(sbrkVal);
// Flatten memory to make it simple to write to. Later passes can
// re-optimize it.
MemoryUtils::ensureExists(module->memory);
if (!MemoryUtils::flatten(module->memory, end, module)) {
Fatal() << "cannot apply sbrk-val since memory is not flattenable\n";
}
auto& segment = module->memory.segments[0];
assert(segment.offset->cast<Const>()->value.geti32() == 0);
assert(end <= segment.data.size());
memcpy(segment.data.data() + sbrkPtr, &sbrkVal, sizeof(sbrkVal));
}
}
// Optimize imports
optimizeImports(runner, module);
// Optimize calls
OptimizeCalls().run(runner, module);
// Optimize exceptions
optimizeExceptions(runner, module);
}
void optimizeImports(PassRunner* runner, Module* module) {
// Calling emscripten_longjmp_jmpbuf is the same as emscripten_longjmp.
Name EMSCRIPTEN_LONGJMP("emscripten_longjmp");
Name EMSCRIPTEN_LONGJMP_JMPBUF("emscripten_longjmp_jmpbuf");
ImportInfo info(*module);
auto* emscripten_longjmp =
info.getImportedFunction(ENV, EMSCRIPTEN_LONGJMP);
auto* emscripten_longjmp_jmpbuf =
info.getImportedFunction(ENV, EMSCRIPTEN_LONGJMP_JMPBUF);
if (emscripten_longjmp && emscripten_longjmp_jmpbuf) {
// Both exist, so it is worth renaming so that we have only one.
emscripten_longjmp_jmpbuf->base = EMSCRIPTEN_LONGJMP;
}
}
// Optimize exceptions (and setjmp) by removing unnecessary invoke* calls.
// An invoke is a call to JS with a function pointer; JS does a try-catch
// and calls the pointer, catching and reporting any error. If we know no
// exception will be thrown, we can simply skip the invoke.
void optimizeExceptions(PassRunner* runner, Module* module) {
// First, check if this code even uses invokes.
bool hasInvokes = false;
for (auto& imp : module->functions) {
if (isInvoke(imp.get())) {
hasInvokes = true;
}
}
if (!hasInvokes) {
return;
}
// Next, see if the Table is flat, which we need in order to see where
// invokes go statically. (In dynamic linking, the table is not flat,
// and we can't do this.)
TableUtils::FlatTable flatTable(module->table);
if (!flatTable.valid) {
return;
}
// This code has exceptions. Find functions that definitely cannot throw,
// and remove invokes to them.
struct Info
: public ModuleUtils::CallGraphPropertyAnalysis<Info>::FunctionInfo {
bool canThrow = false;
};
ModuleUtils::CallGraphPropertyAnalysis<Info> analyzer(
*module, [&](Function* func, Info& info) {
if (func->imported()) {
// Assume any import can throw. We may want to reduce this to just
// longjmp/cxa_throw/etc.
info.canThrow = true;
}
});
// Assume an indirect call might throw.
analyzer.propagateBack(
[](const Info& info) { return info.canThrow; },
[](const Info& info) { return true; },
[](Info& info, Function* reason) { info.canThrow = true; },
analyzer.IndirectCallsHaveProperty);
// Apply the information.
struct OptimizeInvokes : public WalkerPass<PostWalker<OptimizeInvokes>> {
bool isFunctionParallel() override { return true; }
Pass* create() override { return new OptimizeInvokes(map, flatTable); }
std::map<Function*, Info>& map;
TableUtils::FlatTable& flatTable;
OptimizeInvokes(std::map<Function*, Info>& map,
TableUtils::FlatTable& flatTable)
: map(map), flatTable(flatTable) {}
void visitCall(Call* curr) {
auto* target = getModule()->getFunction(curr->target);
if (isInvoke(target)) {
// The first operand is the function pointer index, which must be
// constant if we are to optimize it statically.
if (auto* index = curr->operands[0]->dynCast<Const>()) {
auto actualTarget = flatTable.names.at(index->value.geti32());
if (!map[getModule()->getFunction(actualTarget)].canThrow) {
// This invoke cannot throw! Make it a direct call.
curr->target = actualTarget;
for (Index i = 0; i < curr->operands.size() - 1; i++) {
curr->operands[i] = curr->operands[i + 1];
}
curr->operands.resize(curr->operands.size() - 1);
}
}
}
}
};
OptimizeInvokes(analyzer.map, flatTable).run(runner, module);
}
};
Pass* createPostEmscriptenPass() { return new PostEmscripten(); }
} // namespace wasm
|
