[turbofan] Properly type the OrderedHashTableHealIndex builtin result.

This unblocks the checks in the SimplifiedLowering that whenever we
store something as TaggedSigned, the input type should at least be
Type::SignedSmall.

Bug: chromium:791245
Change-Id: Ice6e55c2c6584c0ff60c1e033ba755c8863af32a
Reviewed-on: https://chromium-review.googlesource.com/808104
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49856}

src/compiler/js-builtin-reducer.cc

@@ -1451,6 +1451,7 @@ Reduction JSBuiltinReducer::ReduceCollectionIteratorNext(
     index = effect = graph()->NewNode(
         common()->Call(desc), jsgraph()->HeapConstant(callable.code()), table,
         index, jsgraph()->NoContextConstant(), effect);
+    NodeProperties::SetType(index, type_cache_.kFixedArrayLengthType);
 
     // Update the {index} and {table} on the {receiver}.
     effect = graph()->NewNode(

test/mjsunit/regress/regress-crbug-791245-1.js

+// Copyright 2017 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
+
+const s = new Map;
+
+function foo(s) {
+  const i = s[Symbol.iterator]();
+  i.next();
+  return i;
+}
+
+console.log(foo(s));
+console.log(foo(s));
+%OptimizeFunctionOnNextCall(foo);
+console.log(foo(s));

test/mjsunit/regress/regress-crbug-791245-2.js

+// Copyright 2017 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
+
+const s = new Set;
+
+function foo(s) {
+  const i = s[Symbol.iterator]();
+  i.next();
+  return i;
+}
+
+console.log(foo(s));
+console.log(foo(s));
+%OptimizeFunctionOnNextCall(foo);
+console.log(foo(s));