[wasm] Exporting i64 globals causes a link error.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2627723007
Cr-Commit-Position: refs/heads/master@{#42333}

src/wasm/wasm-module.cc

@@ -1923,6 +1923,10 @@ class WasmInstanceBuilder {
             case kWasmF64:
               num = *GetRawGlobalPtr<double>(global);
               break;
+            case kWasmI64:
+              thrower_->LinkError(
+                  "export of globals of type I64 is not allowed.");
+              break;
             default:
               UNREACHABLE();
           }

test/mjsunit/wasm/globals.js

@@ -44,6 +44,17 @@ TestExported(kWasmI32, 455.5, 455);
 TestExported(kWasmF32, -999.34343, Math.fround(-999.34343));
 TestExported(kWasmF64, 87347.66666, 87347.66666);
 
+(function TestI64Exported() {
+  var builder = new WasmModuleBuilder();
+  var sig = makeSig([kWasmI64], []);
+  builder.addGlobal(kWasmI32);  // pad
+  var g = builder.addGlobal(kWasmI64, false)
+      .exportAs("foo");
+  g.init = 1234;
+  builder.addGlobal(kWasmI32);  // pad
+
+  assertThrows(()=> {builder.instantiate()}, WebAssembly.LinkError);
+})();
 
 function TestImportedExported(type, val, expected) {
   print("TestImportedExported " + type + "(" + val +")" + " = " + expected);

test/mjsunit/wasm/wasm-module-builder.js

@@ -359,7 +359,7 @@ class WasmModuleBuilder {
               break;
             case kWasmI64:
               section.emit_u8(kExprI64Const);
-              section.emit_u8(global.init);
+              section.emit_u32v(global.init);
               break;
             case kWasmF32:
               section.emit_u8(kExprF32Const);