3 files changed, 63 insertions, 62 deletions

diff --git a/src/asm2wasm-main.cpp b/src/asm2wasm-main.cpp
index 7c4d93052..1e9dc6680 100644
--- a/src/asm2wasm-main.cpp
+++ b/src/asm2wasm-main.cpp
@@ -27,24 +27,8 @@ int main(int argc, char **argv) {
   fclose(f);
   input[num] = 0;
 
-  // emcc --separate-asm modules look like
-  //
-  //    Module["asm"] = (function(global, env, buffer) {
-  //      ..
-  //    });
-  //
-  // we need to clean that up.
-  if (*input == 'M') {
-    while (*input != 'f') {
-      input++;
-      num--;
-    }
-    char *end = input + num - 1;
-    while (*end != '}') {
-      *end = 0;
-      end--;
-    }
-  }
+  Asm2WasmPreProcessor pre;
+  input = pre.process(input);
 
   if (debug) std::cerr << "parsing...\n";
   cashew::Parser<Ref, DotZeroValueBuilder> builder;
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 976e0afe1..187bfeee6 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -82,6 +82,62 @@ struct AstStackHelper {
 std::vector<Ref> AstStackHelper::astStack;
 
 //
+// Asm2WasmPreProcessor - does some initial parsing/processing
+// of asm.js code.
+//
+
+struct Asm2WasmPreProcessor {
+  bool memoryGrowth = false;
+
+  char* process(char* input) {
+    // emcc --separate-asm modules can look like
+    //
+    //    Module["asm"] = (function(global, env, buffer) {
+    //      ..
+    //    });
+    //
+    // we need to clean that up.
+    if (*input == 'M') {
+      size_t num = strlen(input);
+      while (*input != 'f') {
+        input++;
+        num--;
+      }
+      char *end = input + num - 1;
+      while (*end != '}') {
+        *end = 0;
+        end--;
+      }
+    }
+
+    // asm.js memory growth uses a quite elaborate pattern. Instead of parsing and
+    // matching it, we do a simpler detection on emscripten's asm.js output format
+    const char* START_FUNCS = "// EMSCRIPTEN_START_FUNCS";
+    char *marker = strstr(input, START_FUNCS);
+    if (marker) {
+      *marker = 0; // look for memory growth code just up to here
+      char *growthSign = strstr(input, "return true;"); // this can only show up in growth code, as normal asm.js lacks "true"
+      if (growthSign) {
+        memoryGrowth = true;
+        // clean out this function, we don't need it
+        char *growthFuncStart = strstr(input, "function ");
+        assert(strstr(growthFuncStart + 1, "function ") == 0); // should be only this one function in this area, so no confusion for us
+        char *growthFuncEnd = strchr(growthSign, '}');
+        assert(growthFuncEnd > growthFuncStart + 5);
+        growthFuncStart[0] = '/';
+        growthFuncStart[1] = '*';
+        growthFuncEnd--;
+        growthFuncEnd[0] = '*';
+        growthFuncEnd[1] = '/';
+      }
+      *marker = START_FUNCS[0];
+    }
+
+    return input;
+  }
+};
+
+//
 // Asm2WasmBuilder - converts an asm.js module into WebAssembly
 //
 
@@ -213,7 +269,7 @@ private:
   }
 
 public:
-  Asm2WasmBuilder(Module& wasm) : wasm(wasm), nextGlobal(8), maxGlobal(1000) {} // XXX sync with emcc
+  Asm2WasmBuilder(Module& wasm) : wasm(wasm), nextGlobal(8), maxGlobal(1000) {}
 
   void processAsm(Ref ast);
   void optimize();
diff --git a/src/wasm-js.cpp b/src/wasm-js.cpp
index bd0ee51a7..fbd3031ee 100644
--- a/src/wasm-js.cpp
+++ b/src/wasm-js.cpp
@@ -36,47 +36,8 @@ extern "C" void EMSCRIPTEN_KEEPALIVE load_asm(char *input) {
   wasmJSDebug = EM_ASM_INT_V({ return !!Module['outside']['WASM_JS_DEBUG'] }); // Set WASM_JS_DEBUG on the outside Module to get debugging
 #endif
 
-  // emcc --separate-asm modules look like
-  //
-  //    Module["asm"] = (function(global, env, buffer) {
-  //      ..
-  //    });
-  //
-  // we need to clean that up.
-  size_t num = strlen(input);
-  assert(*input == 'M');
-  while (*input != 'f') {
-    input++;
-    num--;
-  }
-  char *end = input + num - 1;
-  while (*end != '}') {
-    *end = 0;
-    end--;
-  }
-
-  // asm.js memory growth uses a quite elaborate pattern. Instead of parsing and
-  // matching it, we do a simpler detection on emscripten's asm.js output format
-  bool memoryGrowth = false;
-  const char* START_FUNCS = "// EMSCRIPTEN_START_FUNCS";
-  char *marker = strstr(input, START_FUNCS);
-  assert(marker && "must have '// EMSCRIPTEN_START_FUNCS' marker (for now)");
-  *marker = 0; // look for memory growth code just up to here
-  char *growthSign = strstr(input, "return true;"); // this can only show up in growth code, as normal asm.js lacks "true"
-  if (growthSign) {
-    memoryGrowth = true;
-    // clean out this function, we don't need it
-    char *growthFuncStart = strstr(input, "function ");
-    assert(strstr(growthFuncStart + 1, "function ") == 0); // should be only this one function in this area, so no confusion for us
-    char *growthFuncEnd = strchr(growthSign, '}');
-    assert(growthFuncEnd > growthFuncStart + 5);
-    growthFuncStart[0] = '/';
-    growthFuncStart[1] = '*';
-    growthFuncEnd--;
-    growthFuncEnd[0] = '*';
-    growthFuncEnd[1] = '/';
-  }
-  *marker = START_FUNCS[0];
+  Asm2WasmPreProcessor pre;
+  input = pre.process(input);
 
   // proceed to parse and wasmify
   if (wasmJSDebug) std::cerr << "parsing...\n";
@@ -88,13 +49,13 @@ extern "C" void EMSCRIPTEN_KEEPALIVE load_asm(char *input) {
   module->memory.initial = EM_ASM_INT_V({
     return Module['providedTotalMemory']; // we receive the size of memory from emscripten
   });
-  module->memory.max = memoryGrowth ? -1 : module->memory.initial;
+  module->memory.max = pre.memoryGrowth ? -1 : module->memory.initial;
 
   if (wasmJSDebug) std::cerr << "wasming...\n";
   asm2wasm = new Asm2WasmBuilder(*module);
   asm2wasm->processAsm(asmjs);
 
-  if (memoryGrowth) {
+  if (pre.memoryGrowth) {
     // create and export a function that just calls memory growth
     auto growWasmMemory = new Function();
     growWasmMemory->name = GROW_WASM_MEMORY;