7 files changed, 90 insertions, 3 deletions
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 23f832506..be3eb3d6d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,6 +36,7 @@ SET(binaryen-shell_SOURCES
   src/passes/LowerIfElse.cpp
   src/passes/NameManager.cpp
   src/passes/RemoveImports.cpp
+  src/passes/RemoveUnusedNames.cpp
 )
 ADD_EXECUTABLE(binaryen-shell
                ${binaryen-shell_SOURCES})
@@ -46,6 +47,8 @@ INSTALL(TARGETS binaryen-shell DESTINATION bin)
 
 SET(asm2wasm_SOURCES
   src/asm2wasm-main.cpp
+  src/pass.cpp
+  src/passes/RemoveUnusedNames.cpp
   src/emscripten-optimizer/parser.cpp
   src/emscripten-optimizer/simple_ast.cpp
   src/emscripten-optimizer/optimizer-shared.cpp
diff --git a/build.sh b/build.sh
index 21934ba01..d883f252c 100755
--- a/build.sh
+++ b/build.sh
@@ -1,8 +1,8 @@
 ./update.py
 echo "building binaryen shell"
-g++ -O2 -std=c++11 src/binaryen-shell.cpp src/pass.cpp src/passes/LowerIfElse.cpp src/passes/NameManager.cpp src/passes/RemoveImports.cpp src/support/colors.cpp -o bin/binaryen-shell -Isrc/ -msse2 -mfpmath=sse # use sse for math, avoid x87, necessarily for proper float rounding on 32-bit
+g++ -O2 -std=c++11 src/binaryen-shell.cpp src/pass.cpp src/passes/LowerIfElse.cpp src/passes/NameManager.cpp src/passes/RemoveImports.cpp src/passes/RemoveUnusedNames.cpp src/support/colors.cpp -o bin/binaryen-shell -Isrc/ -msse2 -mfpmath=sse # use sse for math, avoid x87, necessarily for proper float rounding on 32-bit
 echo "building asm2wasm"
-g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/asm2wasm
+g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/passes/RemoveUnusedNames.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/asm2wasm
 echo "building wasm2asm"
 g++ -O2 -std=c++11 src/wasm2asm-main.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/wasm2asm
 echo "building s2wasm"
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index e37751a66..ce935666e 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -27,6 +27,7 @@
 #include "mixed_arena.h"
 #include "shared-constants.h"
 #include "asm_v_wasm.h"
+#include "pass.h"
 
 namespace wasm {
 
@@ -1566,6 +1567,12 @@ void Asm2WasmBuilder::optimize() {
   for (auto pair : wasm.functionsMap) {
     blockBreakOptimizer.startWalk(pair.second);
   }
+
+  // Standard passes
+
+  PassRunner passRunner(&allocator);
+  passRunner.add("remove-unused-names");
+  passRunner.run(&wasm);
 }
 
 } // namespace wasm
diff --git a/src/pass.cpp b/src/pass.cpp
index 59f51df09..1d3c2d67d 100644
--- a/src/pass.cpp
+++ b/src/pass.cpp
@@ -54,7 +54,9 @@ std::string PassRegistry::getPassDescription(std::string name) {
 // PassRunner
 
 void PassRunner::add(std::string passName) {
-  passes.push_back(PassRegistry::get()->createPass(passName));
+  auto pass = PassRegistry::get()->createPass(passName);
+  assert(pass);
+  passes.push_back(pass);
 }
 
 template<class P>
diff --git a/src/passes/RemoveUnusedNames.cpp b/src/passes/RemoveUnusedNames.cpp
new file mode 100644
index 000000000..9c0b4a83f
--- /dev/null
+++ b/src/passes/RemoveUnusedNames.cpp
@@ -0,0 +1,50 @@
+/*
+ * 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 names from locations that are never branched to.
+//
+
+#include <wasm.h>
+#include <pass.h>
+
+namespace wasm {
+
+struct RemoveUnusedNames : public Pass {
+  std::set<Name> used;
+
+  void prepare(PassRunner* runner, Module *module) override {
+    struct Scanner : public WasmWalker {
+      std::set<Name>& used;
+      Scanner(std::set<Name>& used) : used(used) {}
+      void visitBreak(Break *curr) override {
+        used.insert(curr->name);
+      }
+    };
+    Scanner scanner(used);
+    scanner.startWalk(module);
+  }
+
+  void visitBlock(Block *curr) override {
+    if (curr->name.is() && used.count(curr->name) == 0) {
+      curr->name = Name();
+    }
+  }
+};
+
+static RegisterPass<RemoveUnusedNames> registerPass("remove-unused-names", "removes names from locations that are never branched to");
+
+} // namespace wasm
diff --git a/test/passes/remove-unused-names.txt b/test/passes/remove-unused-names.txt
new file mode 100644
index 000000000..eef6527e7
--- /dev/null
+++ b/test/passes/remove-unused-names.txt
@@ -0,0 +1,16 @@
+(module
+  (memory 16777216 16777216)
+  (func $b0 (param $i1 i32) (result i32)
+    (block $topmost
+      (i32.const 0)
+    )
+  )
+)
+(module
+  (memory 16777216 16777216)
+  (func $b0 (param $i1 i32) (result i32)
+    (block
+      (i32.const 0)
+    )
+  )
+)
diff --git a/test/passes/remove-unused-names.wast b/test/passes/remove-unused-names.wast
new file mode 100644
index 000000000..ae6b2d31b
--- /dev/null
+++ b/test/passes/remove-unused-names.wast
@@ -0,0 +1,9 @@
+(module
+  (memory 16777216 16777216)
+  (func $b0 (param $i1 i32) (result i32)
+    (block $topmost
+      (i32.const 0)
+    )
+  )
+)
+