2 files changed, 32 insertions, 3 deletions

diff --git a/src/js/wasm.js-post.js b/src/js/wasm.js-post.js
index 1c207b3f3..5a1de4c9e 100644
--- a/src/js/wasm.js-post.js
+++ b/src/js/wasm.js-post.js
@@ -29,6 +29,7 @@ function integrateWasmJS(Module) {
   // inputs
 
   var method = Module['wasmJSMethod'] || {{{ wasmJSMethod }}} || 'native-wasm,interpret-s-expr'; // by default, try native and then .wast
+  Module['wasmJSMethod'] = method;
 
   var wasmTextFile = Module['wasmTextFile'] || {{{ wasmTextFile }}};
   var wasmBinaryFile = Module['wasmBinaryFile'] || {{{ wasmBinaryFile }}};
@@ -100,10 +101,12 @@ function integrateWasmJS(Module) {
     }
     var oldView = new Int8Array(oldBuffer);
     var newView = new Int8Array(newBuffer);
-    if ({{{ WASM_BACKEND }}}) {
-      // memory segments arrived in the wast, do not trample them
+
+    // If we have a mem init file, do not trample it
+    if (!memoryInitializer) {
       oldView.set(newView.subarray(STATIC_BASE, STATIC_BASE + STATIC_BUMP), STATIC_BASE);
     }
+
     newView.set(oldView);
     updateGlobalBuffer(newBuffer);
     updateGlobalBufferViews();
@@ -215,6 +218,10 @@ function integrateWasmJS(Module) {
     info.global = global;
     info.env = env;
 
+    if (!('memInitBase' in env)) {
+      env['memInitBase'] = STATIC_BASE; // tell the memory segments where to place themselves
+    }
+
     wasmJS['providedTotalMemory'] = Module['buffer'].byteLength;
 
     // Prepare to generate wasm, using either asm2wasm or s-exprs
diff --git a/src/tools/asm2wasm.cpp b/src/tools/asm2wasm.cpp
index beacc884c..af2cf6f5a 100644
--- a/src/tools/asm2wasm.cpp
+++ b/src/tools/asm2wasm.cpp
@@ -21,6 +21,7 @@
 #include "support/colors.h"
 #include "support/command-line.h"
 #include "support/file.h"
+#include "wasm-builder.h"
 #include "wasm-printing.h"
 
 #include "asm2wasm.h"
@@ -40,10 +41,14 @@ int main(int argc, const char *argv[]) {
              o->extra["output"] = argument;
              Colors::disable();
            })
-      .add("--mapped-globals", "-m", "Mapped globals", Options::Arguments::One,
+      .add("--mapped-globals", "-n", "Mapped globals", Options::Arguments::One,
            [](Options *o, const std::string &argument) {
              std::cerr << "warning: the --mapped-globals/-m option is deprecated (a mapped globals file is no longer needed as we use wasm globals)" << std::endl;
            })
+      .add("--mem-init", "-t", "Import a memory initialization file into the output module", Options::Arguments::One,
+           [](Options *o, const std::string &argument) {
+             o->extra["mem init"] = argument;
+           })
       .add("--total-memory", "-m", "Total memory size", Options::Arguments::One,
            [](Options *o, const std::string &argument) {
              o->extra["total memory"] = argument;
@@ -91,6 +96,23 @@ int main(int argc, const char *argv[]) {
   Asm2WasmBuilder asm2wasm(wasm, pre.memoryGrowth, options.debug, imprecise, opts);
   asm2wasm.processAsm(asmjs);
 
+  // import mem init file, if provided
+  const auto &memInit = options.extra.find("mem init");
+  if (memInit != options.extra.end()) {
+    auto filename = memInit->second.c_str();
+    auto data(read_file<std::vector<char>>(filename, Flags::Binary, options.debug ? Flags::Debug : Flags::Release));
+    // the mem init's base is imported
+    auto* import = new Import;
+    import->name = Name("memInitBase");
+    import->module = Name("env");
+    import->base = Name("memInitBase");
+    import->kind = Import::Global;
+    import->globalType = i32;
+    wasm.addImport(import);
+    // create the memory segment
+    wasm.memory.segments.emplace_back(Builder(wasm).makeGetGlobal(import->name, import->globalType), data);
+  }
+
   if (options.debug) std::cerr << "printing..." << std::endl;
   Output output(options.extra["output"], Flags::Text, options.debug ? Flags::Debug : Flags::Release);
   WasmPrinter::printModule(&wasm, output.getStream());