[wasm] Do not create special wrappers for i64 imports on 32-bit platforms

Wrapper creation for import functions with i64 return values on 32-bit
platforms crashed because the number of return values of the wrapper
did not match the number of input nodes of the return node.

The issue is fixed by not creating special wrappers for 32-bit platforms
in the first place. This is valid because wrappers with i64 return
values are never actually executed.

R=titzer@chromium.org
BUG=v8:5661

Review-Url: https://codereview.chromium.org/2517173003
Cr-Commit-Position: refs/heads/master@{#41190}

src/compiler/wasm-compiler.cc

@@ -2785,16 +2785,8 @@ void WasmGraphBuilder::BuildWasmToJSWrapper(Handle<JSReceiver> target,
       FromJS(call, HeapConstant(isolate->native_context()),
              sig->return_count() == 0 ? wasm::kAstStmt : sig->GetReturn());
   Node* pop_size = jsgraph()->Int32Constant(0);
-  if (jsgraph()->machine()->Is32() && sig->return_count() > 0 &&
-      sig->GetReturn() == wasm::kAstI64) {
-    ret = graph()->NewNode(jsgraph()->common()->Return(), pop_size, val,
-                           graph()->NewNode(jsgraph()->machine()->Word32Sar(),
-                                            val, jsgraph()->Int32Constant(31)),
-                           call, start);
-  } else {
     ret = graph()->NewNode(jsgraph()->common()->Return(), pop_size, val, call,
                            start);
-  }
 
   MergeControlToEnd(jsgraph(), ret);
 }