3 files changed, 51 insertions, 1 deletions
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 2f18b98f1..910134024 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -1606,6 +1606,7 @@ void Asm2WasmBuilder::optimize() {
   passRunner.add("optimize-instructions");
   passRunner.add("simplify-locals");
   passRunner.add("reorder-locals");
+  passRunner.add("vacuum");
   if (maxGlobal < 1024) {
     passRunner.add("post-emscripten");
   }
diff --git a/src/binaryen-shell.cpp b/src/binaryen-shell.cpp
index 14cc66406..7f5b3077e 100644
--- a/src/binaryen-shell.cpp
+++ b/src/binaryen-shell.cpp
@@ -177,7 +177,8 @@ int main(int argc, const char* argv[]) {
   static const char* default_passes[] = {"remove-unused-brs",
                                          "remove-unused-names", "merge-blocks",
                                          "optimize-instructions",
-                                         "simplify-locals", "reorder-locals"};
+                                         "simplify-locals", "reorder-locals",
+                                         "vacuum"};
 
   Options options("binaryen-shell", "Execute .wast files");
   options
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
+