[interpreter] Fix peephole rule on eliding last before jump.

BUG=chromium:629792
LOG=N

Review-Url: https://codereview.chromium.org/2185123003
Cr-Commit-Position: refs/heads/master@{#38140}

src/interpreter/bytecode-peephole-optimizer.cc

@@ -329,12 +329,11 @@ void BytecodePeepholeOptimizer::ElideLastBeforeJumpAction(
     BytecodeNode* const node, const PeepholeActionAndData* action_data) {
   DCHECK(LastIsValid());
   DCHECK(Bytecodes::IsJump(node->bytecode()));
-  DCHECK(CanElideLastBasedOnSourcePosition(node));
 
-  if (!node->source_info().is_valid()) {
-    node->source_info().Clone(last()->source_info());
-  } else {
+  if (!CanElideLastBasedOnSourcePosition(node)) {
     next_stage()->Write(last());
+  } else if (!node->source_info().is_valid()) {
+    node->source_info().Clone(last()->source_info());
   }
   InvalidateLast();
 }

test/mjsunit/ignition/regress-629792-source-position-on-jump.js

+// Copyright 2016 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.
+
+function f(t) {
+  var f = t || this;
+  for (var i in t) {
+    for (var j in t) {
+      (j);
+      continue;
+    }
+  }
+}
+f();