2 files changed, 74 insertions, 3 deletions
diff --git a/src/ast/global-utils.h b/src/ast/global-utils.h
new file mode 100644
index 000000000..f5bebe8aa
--- /dev/null
+++ b/src/ast/global-utils.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2017 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.
+ */
+
+#ifndef wasm_ast_global_h
+#define wasm_ast_global_h
+
+#include <algorithm>
+#include <vector>
+
+#include "literal.h"
+#include "wasm.h"
+
+namespace wasm {
+
+namespace GlobalUtils {
+  // find a global initialized to the value of an import, or null if no such global
+  inline Global* getGlobalInitializedToImport(Module&wasm, Name module, Name base) {
+    // find the import
+    Name imported;
+    for (auto& import : wasm.imports) {
+      if (import->module == module && import->base == base) {
+        imported = import->name;
+        break;
+      }
+    }
+    if (imported.isNull()) return nullptr;
+    // find a global inited to it
+    for (auto& global : wasm.globals) {
+      if (auto* init = global->init->dynCast<GetGlobal>()) {
+        if (init->name == imported) {
+          return global.get();
+        }
+      }
+    }
+    return nullptr;
+  }
+};
+
+} // namespace wasm
+
+#endif // wasm_ast_global_h
+
diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 160e4a4f2..67c9f9707 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -32,6 +32,7 @@
 #include "wasm-interpreter.h"
 #include "wasm-builder.h"
 #include "ast/memory-utils.h"
+#include "ast/global-utils.h"
 
 using namespace wasm;
 
@@ -153,10 +154,14 @@ public:
     // prepare scratch memory
     stack.resize(STACK_SIZE);
     // fill usable values for stack imports
-    auto total = STACK_START + STACK_SIZE;
-    globals["STACKTOP"] = Literal(int32_t(STACK_START));
-    globals["STACK_MAX"] = Literal(int32_t(STACK_START + STACK_SIZE));
+    if (auto* stackTop = GlobalUtils::getGlobalInitializedToImport(wasm, "env", "STACKTOP")) {
+      globals[stackTop->name] = Literal(int32_t(STACK_START));
+    }
+    if (auto* stackMax = GlobalUtils::getGlobalInitializedToImport(wasm, "env", "STACK_MAX")) {
+      globals[stackMax->name] = Literal(int32_t(STACK_START));
+    }
     // tell the module to accept writes up to the stack end
+    auto total = STACK_START + STACK_SIZE;
     memorySize = total / Memory::kPageSize;
   }
 
@@ -398,6 +403,17 @@ int main(int argc, const char* argv[]) {
   }
   evalCtors(wasm, ctors);
 
+  // Do some useful optimizations after the evalling
+  {
+    PassRunner passRunner(&wasm);
+    passRunner.add("memory-packing"); // we flattened it, so re-optimize
+    passRunner.add("remove-unused-names");
+    passRunner.add("dce");
+    passRunner.add("merge-blocks");
+    passRunner.add("vacuum");
+    passRunner.run();
+  }
+
   if (options.extra.count("output") > 0) {
     if (options.debug) std::cerr << "writing..." << std::endl;
     ModuleWriter writer;