Merge pull request #319 from WebAssembly/traversal

Refactor traversal into its own header

1 files changed, 48 insertions, 0 deletions

diff --git a/src/passes/Vacuum.cpp b/src/passes/Vacuum.cpp
new file mode 100644
index 000000000..f9704ed8d
--- /dev/null
+++ b/src/passes/Vacuum.cpp
@@ -0,0 +1,48 @@
+/*
+ * 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>
+
+namespace wasm {
+
+struct Vacuum : public WalkerPass<WasmWalker<Vacuum>> {
+  void visitBlock(Block *curr) {
+    // compress out nops
+    int skip = 0;
+    auto& list = curr->list;
+    size_t size = list.size();
+    for (size_t z = 0; z < size; z++) {
+      if (list[z]->is<Nop>()) {
+        skip++;
+      } else if (skip > 0) {
+        list[z - skip] = list[z];
+      }
+    }
+    if (skip > 0) {
+      list.resize(size - skip);
+    }
+  }
+};
+
+static RegisterPass<Vacuum> registerPass("vacuum", "removes obviously unneeded code");
+
+} // namespace wasm
+