Improve dead code elimination by transitively marking live code and removing all dead code. Replace…

test/mjsunit/compiler/dead-code.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function F() { }
-
-function GrowNamed(o) {
-  o.a = 1;
-  o.b = 2;
-  o.c = 3;
-  o.d = 4;
-  o.e = 5;
-  o.f = 6;
+function dead1(a, b) {
+    var x = a + b;
+    return a; // x is dead
 }
 
-function GrowKeyed(o) {
-  var names = ['a','b','c','d','e','f'];
-  var i = 0;
-  o[names[i++]] = i;
-  o[names[i++]] = i;
-  o[names[i++]] = i;
-  o[names[i++]] = i;
-  o[names[i++]] = i;
-  o[names[i++]] = i;
+function dead2(a, b) {
+    var x = a | 0;
+    var y = b | 0;
+    return a; // x and y are both dead
 }
 
-GrowNamed(new F());
-GrowNamed(new F());
-GrowNamed(new F());
-GrowKeyed(new F());
-GrowKeyed(new F());
-GrowKeyed(new F());
+function dead3(a, b) {
+    var z;
+    if(a == 2) z = a;
+    else z = b;
+    return a; // z is dead
+}
+
+function dead4(a) {
+    var z = 3;
+    for (i = 0; i < 3; i++) {
+        z++;
+    }
+    return a; // z is dead
+}
+
+function dead5(a) {
+    var z = 3;
+    for (i = 0; i < 3; i++) {
+        z++;
+    }
+    var w = z + a;
+    return a; // z is dead
+}
+
+assertTrue(dead1(33, 32) == 33);
+assertTrue(dead2(33, 32) == 33);
+assertTrue(dead3(33, 32) == 33);
+assertTrue(dead4(33) == 33);
+assertTrue(dead5(33) == 33);
+
+assertTrue(dead1(34, 7) == 34);
+assertTrue(dead2(34, 7) == 34);
+assertTrue(dead3(34, 7) == 34);
+assertTrue(dead4(34) == 34);
+assertTrue(dead5(34) == 34);
+
+assertTrue(dead1(3.4, 0.1) == 3.4);
+assertTrue(dead2(3.4, 0.1) == 3.4);
+assertTrue(dead3(3.4, 0.1) == 3.4);
+assertTrue(dead4(3.4) == 3.4);
+assertTrue(dead5(3.4) == 3.4);