Implement graph trimming in ControlReducer.

test/mjsunit/asm/if-folding.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 if0() {
+    if (0) return 11;
+    return 12;
+  }
+
+  function if1() {
+    if (1) return 13;
+    return 14;
+  }
+
+  function if2() {
+    if (0) return 15;
+    else return 16;
+  }
+
+  function if3() {
+    if (1) return 17;
+    else return 18;
+  }
+
+  function if4() {
+    return 1 ? 19 : 20;
+  }
+
+  function if5() {
+    return 0 ? 21 : 22;
+  }
+
+  function if6() {
+    var x = 0 ? 23 : 24;
+    return x;
+  }
+
+  function if7() {
+    if (0) { var x = 0 ? 25 : 26; }
+    else { var x = 0 ? 27 : 28; }
+    return x;
+  }
+
+  function if8() {
+    if (0) {
+      if (0) { var x = 0 ? 29 : 30; }
+      else { var x = 0 ? 31 : 32; }
+    } else {
+      if (0) { var x = 0 ? 33 : 34; }
+      else { var x = 0 ? 35 : 36; }
+    }
+    return x;
+  }
+
+  return {if0: if0, if1: if1, if2: if2, if3: if3, if4: if4, if5: if5, if6: if6, if7: if7, if8: if8 };
+}
+
+var m = Module();
+assertEquals(12, m.if0());
+assertEquals(13, m.if1());
+assertEquals(16, m.if2());
+assertEquals(17, m.if3());
+assertEquals(19, m.if4());
+assertEquals(22, m.if5());
+assertEquals(24, m.if6());
+assertEquals(28, m.if7());
+assertEquals(36, m.if8());
+
+
+function Spec(a,b,c) {
+  "use asm";
+
+  var xx = a | 0;
+  var yy = b | 0;
+  var zz = c | 0;
+
+  function f() {
+    if (xx) {
+      if (yy) { var x = zz ? 29 : 30; }
+      else { var x = zz ? 31 : 32; }
+    } else {
+      if (yy) { var x = zz ? 33 : 34; }
+      else { var x = zz ? 35 : 36; }
+    }
+    return x;
+  }
+  return {f: f};
+}
+
+assertEquals(36, Spec(0,0,0).f());
+assertEquals(35, Spec(0,0,1).f());
+assertEquals(34, Spec(0,1,0).f());
+assertEquals(33, Spec(0,1,1).f());
+assertEquals(32, Spec(1,0,0).f());
+assertEquals(31, Spec(1,0,1).f());
+assertEquals(30, Spec(1,1,0).f());
+assertEquals(29, Spec(1,1,1).f());