[turbofan] Add proper type guards to escape analysis.

test/mjsunit/regress/regress-crbug-640497.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.
 
 // Flags: --allow-natives-syntax --turbo --turbo-escape
 
-function f() {
-  try {
-    throw "boom";
-  } catch(e) {
-    %_DeoptimizeNow();
-  }
-}
+// Warm up {g} with arrays and strings.
+function g(v) { return v.length; }
+assertEquals(1, g("x"));
+assertEquals(2, g("xy"));
+assertEquals(1, g([1]));
+assertEquals(2, g([1,2]));
 
+// Inline into {f}, where we see only an array.
+function f() { assertEquals(0, g([])); }
 f();
 f();
 %OptimizeFunctionOnNextCall(f);
 f();