1 /*
2 * Copyright 2019 WebAssembly Community Group participants
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef wasm_ir_table_h
18 #define wasm_ir_table_h
19
20 #include "ir/literal-utils.h"
21 #include "wasm-traversal.h"
22 #include "wasm.h"
23
24 namespace wasm {
25
26 namespace TableUtils {
27
28 struct FlatTable {
29 std::vector<Name> names;
30 bool valid;
31
FlatTableFlatTable32 FlatTable(Table& table) {
33 valid = true;
34 for (auto& segment : table.segments) {
35 auto offset = segment.offset;
36 if (!offset->is<Const>()) {
37 // TODO: handle some non-constant segments
38 valid = false;
39 return;
40 }
41 Index start = offset->cast<Const>()->value.geti32();
42 Index end = start + segment.data.size();
43 if (end > names.size()) {
44 names.resize(end);
45 }
46 for (Index i = 0; i < segment.data.size(); i++) {
47 names[start + i] = segment.data[i];
48 }
49 }
50 }
51 };
52
getSingletonSegment(Table & table,Module & wasm)53 inline Table::Segment& getSingletonSegment(Table& table, Module& wasm) {
54 if (table.segments.size() != 1) {
55 Fatal() << "Table doesn't have a singleton segment.";
56 }
57 return table.segments[0];
58 }
59
60 // Appends a name to the table. This assumes the table has 0 or 1 segments,
61 // as with 2 or more it's ambiguous what we should do (use a hole in the middle
62 // or not).
63 // This works on code from wasm-ld, but on arbitrary code it may not be valid
64 // in the presence of a dynamic linking section. Specifically, we assume the
65 // module has a single table segment, and that the dylink section indicates
66 // we can validly append to that segment, see the check below.
append(Table & table,Name name,Module & wasm)67 inline Index append(Table& table, Name name, Module& wasm) {
68 auto& segment = getSingletonSegment(table, wasm);
69 auto tableIndex = segment.data.size();
70 if (wasm.dylinkSection) {
71 if (segment.data.size() != wasm.dylinkSection->tableSize) {
72 Fatal() << "Appending to the table in a module with a dylink section "
73 "that has tableSize which indicates it wants to reserve more "
74 "table space than the actual table elements in the module. "
75 "We don't know how to correctly update the dylink section in "
76 "that case.";
77 }
78 wasm.dylinkSection->tableSize++;
79 }
80 segment.data.push_back(name);
81 table.initial = table.initial + 1;
82 return tableIndex;
83 }
84
85 // Checks if a function is already in the table. Returns that index if so,
86 // otherwise appends it.
getOrAppend(Table & table,Name name,Module & wasm)87 inline Index getOrAppend(Table& table, Name name, Module& wasm) {
88 auto& segment = getSingletonSegment(table, wasm);
89 for (Index i = 0; i < segment.data.size(); i++) {
90 if (segment.data[i] == name) {
91 return i;
92 }
93 }
94 return append(table, name, wasm);
95 }
96
97 } // namespace TableUtils
98
99 } // namespace wasm
100
101 #endif // wasm_ir_table_h
102