[turbofan] Fix control reducer for degenerate cases of self-loop branches.

test/mjsunit/regress/regress-447526.js

Index: test/mjsunit/regress/regress-447526.js
diff --git a/test/mjsunit/regress/regress-3392.js b/test/mjsunit/regress/regress-447526.js
similarity index 65%
copy from test/mjsunit/regress/regress-3392.js
copy to test/mjsunit/regress/regress-447526.js
index 375f30210ce11272799c78b51463d97fc6b65998..9f9396f2eeae9ca6fd32d79818895cf433d58a18 100644
--- a/test/mjsunit/regress/regress-3392.js
+++ b/test/mjsunit/regress/regress-447526.js
@@ -4,15 +4,22 @@
 
 // Flags: --allow-natives-syntax
 
+function bar() {
+  throw "done";
+}
+
 function foo() {
-  var a = {b: -1.5};
-  for (var i = 0; i < 1; i++) {
-    a.b = 1;
+  var i;
+  while (i) {
+    while (i) {
+}
+    i++;
+  }
+  while (true) {
+    bar();
   }
-  assertTrue(0 <= a.b);
 }
 
-foo();
-foo();
+
 %OptimizeFunctionOnNextCall(foo);
-foo();
+assertThrows(foo);