Improve and simplify removal of unreachable code

test/mjsunit/constant-branch-folding-liveness.js

Index: test/mjsunit/constant-branch-folding-liveness.js
diff --git a/test/mjsunit/regress/regress-2813.js b/test/mjsunit/constant-branch-folding-liveness.js
similarity index 81%
copy from test/mjsunit/regress/regress-2813.js
copy to test/mjsunit/constant-branch-folding-liveness.js
index 97ae43b316a2177596927cf5465fa2214cc11c61..ca3fdc774606bfa56669b8a3b289af9845176ff3 100644
--- a/test/mjsunit/regress/regress-2813.js
+++ b/test/mjsunit/constant-branch-folding-liveness.js
@@ -27,18 +27,21 @@
 
 // Flags: --allow-natives-syntax
 
-function foo(x) {
+function funky() { return false; }
+var global;
+
+function foo(x, fun) {
   var a = x + 1;
-  var b = x + 2;
-  if (x != 0) {
-    if (x > 0 & x < 100) {
-      return a;
-    }
+  var b = x + 2;  // Need another Simulate to fold the first one into.
+  global = true;  // Need a side effect to deopt to.
+  if (fun()) {
+    return a;
   }
   return 0;
 }
 
-assertEquals(0, foo(0));
-assertEquals(0, foo(0));
+assertEquals(0, foo(1, funky));
+assertEquals(0, foo(1, funky));
 %OptimizeFunctionOnNextCall(foo);
-assertEquals(3, foo(2));
+assertEquals(0, foo(1, funky));
+assertEquals(2, foo(1, function() { return true; }));