src/binaryen/src/passes/ReorderFunctions.cpp

   1 /*
   2  * Copyright 2016 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 //
  18 // Sorts functions by their static use count. This helps reduce the size of wasm
  19 // binaries because fewer bytes are needed to encode references to frequently
  20 // used functions.
  21 //
  22
  23
  24 #include <memory>
  25
  26 #include <wasm.h>
  27 #include <pass.h>
  28
  29 namespace wasm {
  30
  31 struct ReorderFunctions : public WalkerPass<PostWalker<ReorderFunctions>> {
  32   std::map<Name, uint32_t> counts;
  33
  34   void visitModule(Module *module) {
  35     if (module->start.is()) {
  36       counts[module->start]++;
  37     }
  38     for (auto& curr : module->exports) {
  39       counts[curr->value]++;
  40     }
  41     for (auto& segment : module->table.segments) {
  42       for (auto& curr : segment.data) {
  43         counts[curr]++;
  44       }
  45     }
  46     std::sort(module->functions.begin(), module->functions.end(), [this](
  47       const std::unique_ptr<Function>& a,
  48       const std::unique_ptr<Function>& b) -> bool {
  49       if (this->counts[a->name] == this->counts[b->name]) {
  50         return strcmp(a->name.str, b->name.str) > 0;
  51       }
  52       return this->counts[a->name] > this->counts[b->name];
  53     });
  54     counts.clear();
  55   }
  56
  57   void visitCall(Call *curr) {
  58     counts[curr->target]++;
  59   }
  60 };
  61
  62 Pass *createReorderFunctionsPass() {
  63   return new ReorderFunctions();
  64 }
  65
  66 } // namespace wasm