Fix IsDeletable() for HStringAdd, HStringCharCodeAt, HStringCharFromCode.

test/mjsunit/compiler/dead-string-char-code-at.js

-// Copyright 2008 the V8 project authors. All rights reserved.
+// Copyright 2013 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.
 
 // Flags: --allow-natives-syntax
-// Test some dead code elimination scenarios
 
-function dead1(x, y) {
-    var a = x | 0, b = y | 0;
-    a * b;
-    a << b;
-    a >> b;
-    a >>> b;
-    a | b;
-    a & b;
-    a ^ b;
-    return x;
+var S1 = "string1";
+var S2 = "@@string2";
+
+function dead1(a, b) {
+    var x = %StringCharCodeAt(a, 4);
+    return a; // x is dead code
 }
 
-function dead2(x, y) {
-    var a = x | 0, b = y | 0;
-    (a | 0) * b;
-    (a | 0) << b;
-    (a | 0) >> b;
-    (a | 0) >>> b;
-    (a | 0) | b;
-    (a | 0) & b;
-    (a | 0) ^ b;
-    return x;
+function dead2(a, b) {
+    var x = %StringCharCodeAt(a, 3);
+    var y = %StringCharCodeAt(b, 1);
+    return a; // x and y are both dead
 }
 
 function dead3(a, b) {
-    a == 2 ? (a * b) : (b * a); // dead
-    return a;
+    a = a ? "11" : "12";
+    b = b ? "13" : "14";
+    var x = %StringCharCodeAt(a, 2);
+    var y = %StringCharCodeAt(b, 0);
+    return a; // x and y are both dead
 }
 
-assertTrue(dead1(33, 32) == 33);
-assertTrue(dead1(33, 32) == 33);
+function test() {
+  var S3 = S1 + S2;
+
+  assertTrue(dead1(S1, S2) == S1);
+  assertTrue(dead2(S1, S2) == S1);
+  assertTrue(dead3(S1, S2) == "11");
+
+  assertTrue(dead1(S2, 677) == S2);
+  assertTrue(dead2(S2, S3) == S2);
+  assertTrue(dead3(S2, S3) == "11");
+
+  assertTrue(dead1(S3, 399) == S3);
+  assertTrue(dead2(S3, "false") == S3);
+  assertTrue(dead3(0, 32) == "12");
+
+  assertTrue(dead1(S3, 0) == S3);
+  assertTrue(dead2(S3, S1) == S3);
+  assertTrue(dead3(S3, 0) == "11");
+
+  assertTrue(dead1("true", 0) == "true");
+  assertTrue(dead2("true", S3) == "true");
+  assertTrue(dead3("true", 0) == "11");
+}
+
+test();
+test();
 %OptimizeFunctionOnNextCall(dead1);
-assertTrue(dead1(33, 32) == 33);
-
-assertTrue(dead2(34, 11) == 34);
-assertTrue(dead2(34, 11) == 34);
 %OptimizeFunctionOnNextCall(dead2);
-assertTrue(dead2(34, 11) == 34);
-
-assertTrue(dead3(35, 12) == 35);
-assertTrue(dead3(35, 12) == 35);
 %OptimizeFunctionOnNextCall(dead3);
-assertTrue(dead3(35, 12) == 35);
+test();