4 files changed, 31 insertions, 0 deletions
diff --git a/src/support/file.h b/src/support/file.h
index c15e3f6ce..8355767ee 100644
--- a/src/support/file.h
+++ b/src/support/file.h
@@ -59,6 +59,10 @@ class Output {
     return out;
   }
 
+  std::ostream& write(const char* s, std::streamsize c) {
+    return out.write(s, c);
+  }
+
  private:
   Output() = delete;
   Output(const Output &) = delete;
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index 4c9f8df36..495ed5df9 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -40,6 +40,7 @@ int main(int argc, const char *argv[]) {
   std::string inputSourceMapFilename;
   std::string outputSourceMapFilename;
   std::string outputSourceMapUrl;
+  std::string dataSegmentFile;
   bool emitBinary = true;
   bool debugInfo = false;
   bool legalizeJavaScriptFFI = true;
@@ -94,6 +95,9 @@ int main(int argc, const char *argv[]) {
       .add("--output-source-map-url", "-osu", "Emit specified string as source map URL",
            Options::Arguments::One,
            [&outputSourceMapUrl](Options *o, const std::string& argument) { outputSourceMapUrl = argument; })
+      .add("--separate-data-segments", "", "Separate data segments to a file",
+           Options::Arguments::One,
+           [&dataSegmentFile](Options *o, const std::string& argument) { dataSegmentFile = argument;})
       .add_positional("INFILE", Options::Arguments::One,
                       [&infile](Options *o, const std::string& argument) {
                         infile = argument;
@@ -161,6 +165,10 @@ int main(int argc, const char *argv[]) {
   generator.generateDynCallThunks();
   generator.generateJSCallThunks(numReservedFunctionPointers);
   std::string metadata = generator.generateEmscriptenMetadata(dataSize, initializerFunctions, numReservedFunctionPointers);
+  if (!dataSegmentFile.empty()) {
+    Output memInitFile(dataSegmentFile, Flags::Binary, Flags::Release);
+    generator.separateDataSegments(&memInitFile);
+  }
 
   if (options.debug) {
     std::cerr << "Module after:\n";
diff --git a/src/wasm-emscripten.h b/src/wasm-emscripten.h
index 21bd21bea..78d24b13f 100644
--- a/src/wasm-emscripten.h
+++ b/src/wasm-emscripten.h
@@ -19,6 +19,8 @@
 
 #include "wasm.h"
 #include "wasm-builder.h"
+#include "support/file.h"
+
 
 namespace wasm {
 
@@ -53,6 +55,8 @@ public:
 
   void fixInvokeFunctionNames();
 
+  void separateDataSegments(Output* outfile);
+
 private:
   Module& wasm;
   Builder builder;
diff --git a/src/wasm/wasm-emscripten.cpp b/src/wasm/wasm-emscripten.cpp
index d7c323da9..a99482d39 100644
--- a/src/wasm/wasm-emscripten.cpp
+++ b/src/wasm/wasm-emscripten.cpp
@@ -810,4 +810,19 @@ std::string EmscriptenGlueGenerator::generateEmscriptenMetadata(
   return meta.str();
 }
 
+void EmscriptenGlueGenerator::separateDataSegments(Output* outfile) {
+  size_t lastEnd = 0;
+  for (Memory::Segment& seg : wasm.memory.segments) {
+    size_t offset = seg.offset->cast<Const>()->value.geti32();
+    size_t fill = offset - lastEnd;
+    if (fill > 0) {
+      std::vector<char> buf(fill);
+      outfile->write(buf.data(), fill);
+    }
+    outfile->write(seg.data.data(), seg.data.size());
+    lastEnd = offset + seg.data.size();
+  }
+  wasm.memory.segments.clear();
+}
+
 } // namespace wasm