Implement graph trimming in ControlReducer.

test/mjsunit/asm/infinite-loops.js

+// 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.
+
+function Module() {
+  "use asm";
+
+  function w0(a) {
+    a = a | 0;
+    if (a) while (1);
+    return 42;
+  }
+
+  function w1(a) {
+    a = a | 0;
+    while (1) return 42;
+    return 106;
+  }
+
+  function d0(a) {
+    a = a | 0;
+    if (a) do ; while(1);
+    return 42;
+  }
+
+  function d1(a) {
+    a = a | 0;
+    do return 42; while(1);
+    return 107;
+  }
+
+  function f0(a) {
+    a = a | 0;
+    if (a) for (;;) ;
+    return 42;
+  }
+
+  function f1(a) {
+    a = a | 0;
+    for(;;) return 42;
+    return 108;
+  }
+
+  return { w0: w0, w1: w1, d0: d0, d1: d1, f0: f0, f1: f1 };
+}
+
+var m = Module();
+assertEquals(42, m.w0(0));
+assertEquals(42, m.w1(0));
+assertEquals(42, m.d0(0));
+assertEquals(42, m.d1(0));
+assertEquals(42, m.f0(0));
+assertEquals(42, m.f1(0));