[wasm] Fix wasm to js wrapper on ia32 for i64 return

When generating the code for an illegal (non-js-compliant) wrapper for
a js function, we were generating a zero constant of the return type.
This failed on ia32 if the return type is i64.
The correct thing to do is to return two i32 zero constants.

R=titzer@chromium.org
BUG=v8:6104, v8:6096

Change-Id: Idc0dd8d3eef901c22d5278d97f1879b000a18588
Reviewed-on: https://chromium-review.googlesource.com/455857Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43835}

src/compiler/wasm-compiler.cc

@@ -2823,9 +2823,14 @@ void WasmGraphBuilder::BuildWasmToJSWrapper(Handle<JSReceiver> target,
     BuildCallToRuntimeWithContext(Runtime::kWasmThrowTypeError, jsgraph(),
                                   context, nullptr, 0, effect_, *control_);
     // TODO(wasm): Support multi-return.
-    wasm::ValueType return_type =
-        sig->return_count() == 0 ? wasm::kWasmI32 : sig->GetReturn();
-    Return(ZeroConstant(return_type));
+    if (sig->return_count() == 0) {
+      Return(Int32Constant(0));
+    } else if (Int64Lowering::IsI64AsTwoParameters(jsgraph()->machine(),
+                                                   sig->GetReturn())) {
+      Return(Int32Constant(0), Int32Constant(0));
+    } else {
+      Return(ZeroConstant(sig->GetReturn()));
+    }
     return;
   }
 

test/mjsunit/wasm/ffi-error.js

@@ -128,6 +128,19 @@ assertThrows(function() {
   assertThrows(() => instance.exports.main(), TypeError);
 })();
 
+(function ImportI64Return() {
+  // This tests that we generate correct code by using the correct return
+  // register(s). See bug 6104.
+  var builder = new WasmModuleBuilder();
+  builder.addImport('', 'f', makeSig([], [kWasmI64]));
+  builder.addFunction('main', kSig_v_v)
+      .addBody([kExprCallFunction, 0, kExprDrop])
+      .exportFunc();
+  var instance = builder.instantiate({'': {f: () => 1}});
+
+  assertThrows(() => instance.exports.main(), TypeError);
+})();
+
 (function ImportSymbolToNumberThrows() {
   var builder = new WasmModuleBuilder();
   var index = builder.addImport("", "func", kSig_i_v);