From 09d082c6780d5bd7642d1c6715f2490b7f542486 Mon Sep 17 00:00:00 2001
From: Sergey Rubanov <chi187@gmail.com>
Date: Wed, 16 Jan 2019 19:53:37 +0300
Subject: [PATCH] Use WebAssembly.instantiateStreaming when presented in
 browser (#2477)

---
 runtime/src/launcher/js/launcher.js | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/runtime/src/launcher/js/launcher.js b/runtime/src/launcher/js/launcher.js
index ac0567daa2d..b2f55c2c9d4 100644
--- a/runtime/src/launcher/js/launcher.js
+++ b/runtime/src/launcher/js/launcher.js
@@ -210,15 +210,27 @@ function instantiateAndRunSync(arraybuffer, args) {
     return invokeModule(instance, args)
 }
 
+
+// Instantiate module in Browser as a promise of streaming instantiation.
+function instantiateAndRunStreaming(filename) {
+    linkJavaScriptLibraries();
+    WebAssembly.instantiateStreaming(fetch(filename), konan_dependencies)
+      .then(resultObject => invokeModule(resultObject.instance, [filename]));
+}
+
 konan.moduleEntry = function (args) {
     if (isBrowser()) {
         if (!document.currentScript.hasAttribute("wasm")) {
             throw new Error('Could not find the wasm attribute pointing to the WebAssembly binary.');
         }
         const filename = document.currentScript.getAttribute("wasm");
-        fetch(filename)
-            .then(response => response.arrayBuffer())
-            .then(arraybuffer => instantiateAndRun(arraybuffer, [filename]));
+        if (typeof WebAssembly.instantiateStreaming === 'function') {
+            instantiateAndRunStreaming(filename);
+        } else {
+            fetch(filename)
+              .then(response => response.arrayBuffer())
+              .then(arraybuffer => instantiateAndRun(arraybuffer, [filename]));
+        }
     } else {
         // Invoke from d8.
         const arrayBuffer = readbuffer(args[0]);