[turbofan] Fix corner case in loop analysis.

test/cctest/compiler/test-loop-analysis.cc

 // Copyright 2014 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.
 
 #include "src/v8.h"
 
 #include "src/compiler/access-builder.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/graph-visualizer.h"
@@ skipping 244 matching lines @@
 
   Node* chain[] = {w.loop};
   t.CheckNestedLoops(chain, 1);
 
   Node* header[] = {w.loop};
   Node* body[] = {w.branch, w.if_true};
   t.CheckLoop(header, 1, body, 2);
 }
 
 
+TEST(LaLoop1phi) {
+  // One loop with a simple phi.
+  LoopFinderTester t;
+  While w(t, t.p0);
+  Node* phi =
+      t.graph.NewNode(t.common.Phi(kMachAnyTagged, 2), t.zero, t.one, w.loop);
+  t.Return(phi, t.start, w.exit);
+
+  Node* chain[] = {w.loop};
+  t.CheckNestedLoops(chain, 1);
+
+  Node* header[] = {w.loop, phi};
+  Node* body[] = {w.branch, w.if_true};
+  t.CheckLoop(header, 2, body, 2);
+}
+
+
 TEST(LaLoop1c) {
   // One loop with a counter.
   LoopFinderTester t;
   While w(t, t.p0);
   Counter c(w, 0, 1);
   t.Return(c.phi, t.start, w.exit);
 
   Node* chain[] = {w.loop};
   t.CheckNestedLoops(chain, 1);
 
@@ skipping 578 matching lines @@
 TEST(LaEdgeMatrix3_2) { RunEdgeMatrix3_i(2); }
 
 
 TEST(LaEdgeMatrix3_3) { RunEdgeMatrix3_i(3); }
 
 
 TEST(LaEdgeMatrix3_4) { RunEdgeMatrix3_i(4); }
 
 
 TEST(LaEdgeMatrix3_5) { RunEdgeMatrix3_i(5); }