RemoveUnusedBrs #32

2 files changed, 42 insertions, 0 deletions

diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index ce935666e..e91a9344e 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -1571,6 +1571,7 @@ void Asm2WasmBuilder::optimize() {
   // Standard passes
 
   PassRunner passRunner(&allocator);
+  passRunner.add("remove-unused-brs");
   passRunner.add("remove-unused-names");
   passRunner.run(&wasm);
 }
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
new file mode 100644
index 000000000..ff50847de
--- /dev/null
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -0,0 +1,41 @@
+/*
+ * 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.
+ */
+
+//
+// Removes branches that go to where they go anyhow
+//
+
+#include <wasm.h>
+#include <pass.h>
+
+namespace wasm {
+
+struct RemoveUnusedBrs : public Pass {
+  void visitBlock(Block *curr) override {
+    if (curr->name.isNull()) return;
+    if (curr->list.size() == 0) return;
+    Break* last = curr->list.back()->dyn_cast<Break>();
+    if (!last) return;
+    if (last->value) return;
+    if (last->name == curr->name) {
+      curr->list.pop_back();
+    }
+  }
+};
+
+static RegisterPass<RemoveUnusedBrs> registerPass("remove-unused-brs", "removes breaks from locations that are never branched to");
+
+} // namespace wasm