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
|
/*
* Copyright 2016 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.
*/
//
// Removes obviously unneeded code
//
#include <wasm.h>
#include <pass.h>
#include <ast_utils.h>
#include <wasm-builder.h>
namespace wasm {
struct Vacuum : public WalkerPass<PostWalker<Vacuum, Visitor<Vacuum>>> {
bool isFunctionParallel() { return true; }
std::vector<Expression*> expressionStack;
bool isDead(Expression* curr, bool resultMayBeUsed) {
if (curr->is<Nop>()) return true;
// dead get_locals may be generated from coalesce-locals
if (curr->is<GetLocal>() && (!resultMayBeUsed || !ExpressionAnalyzer::isResultUsed(expressionStack, getFunction()))) return true;
// TODO: more dead code
return false;
}
void visitBlock(Block *curr) {
// compress out nops and other dead code
int skip = 0;
auto& list = curr->list;
size_t size = list.size();
bool needResize = false;
for (size_t z = 0; z < size; z++) {
if (isDead(list[z], z == size - 1)) {
skip++;
needResize = true;
} else {
if (skip > 0) {
list[z - skip] = list[z];
}
// if this is an unconditional br, the rest is dead code
Break* br = list[z - skip]->dynCast<Break>();
Switch* sw = list[z - skip]->dynCast<Switch>();
if ((br && !br->condition) || sw) {
list.resize(z - skip + 1);
needResize = false;
break;
}
}
}
if (needResize) {
list.resize(size - skip);
}
if (!curr->name.is()) {
if (list.size() == 1) {
replaceCurrent(list[0]);
} else if (list.size() == 0) {
ExpressionManipulator::nop(curr);
}
}
}
void visitIf(If* curr) {
if (curr->ifFalse) {
if (curr->ifFalse->is<Nop>()) {
curr->ifFalse = nullptr;
} else if (curr->ifTrue->is<Nop>()) {
curr->ifTrue = curr->ifFalse;
curr->ifFalse = nullptr;
curr->condition = Builder(*getModule()).makeUnary(EqZInt32, curr->condition);
}
}
if (!curr->ifFalse) {
// no else
if (curr->ifTrue->is<Nop>()) {
// no nothing
replaceCurrent(curr->condition);
}
}
}
static void visitPre(Vacuum* self, Expression** currp) {
self->expressionStack.push_back(*currp);
}
static void visitPost(Vacuum* self, Expression** currp) {
self->expressionStack.pop_back();
}
// override scan to add a pre and a post check task to all nodes
static void scan(Vacuum* self, Expression** currp) {
self->pushTask(visitPost, currp);
WalkerPass<PostWalker<Vacuum, Visitor<Vacuum>>>::scan(self, currp);
self->pushTask(visitPre, currp);
}
};
static RegisterPass<Vacuum> registerPass("vacuum", "removes obviously unneeded code");
} // namespace wasm
|
