Code folding (#1076)

Adds a pass that folds code, i.e. merges it when possible. See details in comment in the pass implementation cpp.

This is enabled by default in -Os and -Oz. Seems risky to enable anywhere else, as it does add branches - likely predictable ones so maybe no slowdown, but still some risk.

Code size numbers:

wasm-backend: 196331
+ binaryen -Os (before): 182598
+ binaryen -Os (with folding): 181943

asm2wasm -Os (before): 172463
asm2wasm -Os (with folding): 168774

So this reduces wasm-backend output by an additional 0.5% than it could before. Mainly this is because the wasm backend already has code folding, whereas on asm2wasm output, where we didn't have folding before, this saves over 2%. The 0.5% improvement on the wasm backend's output might be because this can fold more types of code than LLVM can (it can fold nested control flow, in particular).

1 files changed, 0 insertions, 80 deletions

diff --git a/src/passes/NameManager.cpp b/src/passes/NameManager.cpp
deleted file mode 100644
index 035586a77..000000000
--- a/src/passes/NameManager.cpp
+++ /dev/null
@@ -1,80 +0,0 @@
-/*
- * 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.
- */
-
-//
-// NameManager
-//
-
-#include <wasm.h>
-#include <pass.h>
-
-namespace wasm {
-
-Name NameManager::getUnique(std::string prefix) {
-  while (1) {
-    Name curr = cashew::IString((prefix + std::to_string(counter++)).c_str(), false);
-    if (names.find(curr) == names.end()) {
-      names.insert(curr);
-      return curr;
-    }
-  }
-}
-
-void NameManager::visitBlock(Block* curr) {
-  names.insert(curr->name);
-}
-void NameManager::visitLoop(Loop* curr) {
-  names.insert(curr->name);
-}
-void NameManager::visitBreak(Break* curr) {
-  names.insert(curr->name);
-}
-void NameManager::visitSwitch(Switch* curr) {
-  names.insert(curr->default_);
-  for (auto& target : curr->targets) {
-    names.insert(target);
-  }
-}
-void NameManager::visitCall(Call* curr) {
-  names.insert(curr->target);
-}
-void NameManager::visitCallImport(CallImport* curr) {
-  names.insert(curr->target);
-}
-void NameManager::visitFunctionType(FunctionType* curr) {
-  names.insert(curr->name);
-}
-void NameManager::visitFunction(Function* curr) {
-  names.insert(curr->name);
-  for (Index i = 0; i < curr->getNumLocals(); i++) {
-    Name name = curr->getLocalNameOrDefault(i);
-    if (name.is()) {
-      names.insert(name);
-    }
-  }
-}
-void NameManager::visitImport(Import* curr) {
-  names.insert(curr->name);
-}
-void NameManager::visitExport(Export* curr) {
-  names.insert(curr->name);
-}
-
-Pass *createNameManagerPass() {
-  return new NameManager();
-}
-
-} // namespace wasm