Regression test for word64-lowered BigInt accumulator

This issue was fixed in https://chromium-review.googlesource.com/c/v8/v8/+/1873692

Bug: chromium:1016450
Change-Id: I56e1c504ae6876283568a88a9aa7d24af3ba6474
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1876057
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Auto-Submit: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64738}

test/mjsunit/regress/regress-1016450.js

+// Copyright 2019 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --opt --no-always-opt
+
+let g = 0;
+
+function f(x) {
+  let y = BigInt.asUintN(64, 15n);
+  // Introduce a side effect to force the construction of a FrameState that
+  // captures the value of y.
+  g = 42;
+  try {
+    return x + y;
+  } catch(_) {
+    return y;
+  }
+}
+
+
+%PrepareFunctionForOptimization(f);
+assertEquals(16n, f(1n));
+assertEquals(17n, f(2n));
+%OptimizeFunctionOnNextCall(f);
+assertEquals(16n, f(1n));
+assertOptimized(f);
+assertEquals(15n, f(0));
+assertUnoptimized(f);