refactor memory allocation code to create the buffer during asm.js link

1 files changed, 41 insertions, 29 deletions

diff --git a/src/js/post.js b/src/js/post.js
index c7d99147f..640c4b93f 100644
--- a/src/js/post.js
+++ b/src/js/post.js
@@ -5,32 +5,6 @@ function integrateWasmJS(Module) {
   // XXX don't be confused. Module here is in the outside program. wasmJS is the inner wasm-js.cpp.
   wasmJS['outside'] = Module; // Inside wasm-js.cpp, Module['outside'] reaches the outside module.
 
-  // Generate a module instance of the asm.js converted into wasm.
-  var code;
-  if (typeof read === 'function') {
-    // spidermonkey or v8 shells
-    code = read(Module['asmjsCodeFile']);
-  } else if (typeof process === 'object' && typeof require === 'function') {
-    // node.js
-    code = require('fs')['readFileSync'](Module['asmjsCodeFile']).toString();
-  } else {
-    throw 'TODO: loading in other platforms';
-  }
-
-  var theBuffer = Module['buffer'] = new ArrayBuffer(Module['providedTotalMemory'] || 64*1024*1024);
-  wasmJS['providedTotalMemory'] = theBuffer.byteLength;
-
-  Module['reallocBuffer'] = function(size) {
-    var old = Module['buffer'];
-    wasmJS['asmExports']['__growWasmMemory'](size); // tiny wasm method that just does grow_memory
-    return Module['buffer'] !== old ? Module['buffer'] : null; // if it was reallocated, it changed
-  };
-
-  var temp = wasmJS['_malloc'](code.length + 1);
-  wasmJS['writeAsciiToMemory'](code, temp);
-  wasmJS['_load_asm'](temp);
-  wasmJS['_free'](temp);
-
   // Information for the instance of the module.
   var info = wasmJS['info'] = {
     global: null,
@@ -65,9 +39,47 @@ function integrateWasmJS(Module) {
     return lookup;
   }
 
-  // The asm.js function, called to "link" the asm.js module.
-  Module['asm'] = function(global, env, buffer) {
-    assert(buffer === Module['buffer']); // we should not even need to pass it as a 3rd arg for wasm, but that's the asm.js way.
+  // The asm.js function, called to "link" the asm.js module. At that time, we are provided imports
+  // and respond with exports, and so forth.
+  Module['asm'] = function(global, env, providedBuffer) {
+    assert(providedBuffer === Module['buffer']); // we should not even need to pass it as a 3rd arg for wasm, but that's the asm.js way.
+
+    // Generate a module instance of the asm.js converted into wasm.
+    var code;
+    if (typeof read === 'function') {
+      // spidermonkey or v8 shells
+      code = read(Module['asmjsCodeFile']);
+    } else if (typeof process === 'object' && typeof require === 'function') {
+      // node.js
+      code = require('fs')['readFileSync'](Module['asmjsCodeFile']).toString();
+    } else {
+      throw 'TODO: loading in other platforms';
+    }
+
+    // wasm code would create its own buffer, at this time. But static init code might have
+    // written to the buffer already, and we must copy it over. We could just avoid
+    // this copy in wasm.js polyfilling, but to be as close as possible to real wasm,
+    // we do what wasm would do.
+    // TODO: avoid this copy, by avoiding such static init writes
+    // TODO: in shorter term, just copy up to the last static init write
+    var oldBuffer = Module['buffer'];
+    var newBuffer = ArrayBuffer(oldBuffer.byteLength);
+    (new Int8Array(newBuffer)).set(new Int8Array(oldBuffer));
+    updateGlobalBuffer(newBuffer);
+    updateGlobalBufferViews();
+    wasmJS['providedTotalMemory'] = Module['buffer'].byteLength;
+
+    Module['reallocBuffer'] = function(size) {
+      var old = Module['buffer'];
+      wasmJS['asmExports']['__growWasmMemory'](size); // tiny wasm method that just does grow_memory
+      return Module['buffer'] !== old ? Module['buffer'] : null; // if it was reallocated, it changed
+    };
+
+    var temp = wasmJS['_malloc'](code.length + 1);
+    wasmJS['writeAsciiToMemory'](code, temp);
+    wasmJS['_load_asm'](temp);
+    wasmJS['_free'](temp);
+
     // write the provided data to a location the wasm instance can get at it.
     info.global = global;
     info.env = env;