Fix IsDeletable() for HStringAdd, HStringCharCodeAt, HStringCharFromCode.

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

Index: test/mjsunit/compiler/dead-string-char-code-at.js
diff --git a/test/mjsunit/compiler/dead-code6.js b/test/mjsunit/compiler/dead-string-char-code-at.js
similarity index 60%
copy from test/mjsunit/compiler/dead-code6.js
copy to test/mjsunit/compiler/dead-string-char-code-at.js
index ec9b8433ddd72187b3f9dab70baf2399fac0cdb2..1989d9d7351cf69d182c7d2a1450f765610bdd80 100644
--- a/test/mjsunit/compiler/dead-code6.js
+++ b/test/mjsunit/compiler/dead-string-char-code-at.js
@@ -1,4 +1,4 @@
-// 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:
@@ -26,48 +26,56 @@
 // 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);
-%OptimizeFunctionOnNextCall(dead1);
-assertTrue(dead1(33, 32) == 33);
+function test() {
+  var S3 = S1 + S2;
 
-assertTrue(dead2(34, 11) == 34);
-assertTrue(dead2(34, 11) == 34);
-%OptimizeFunctionOnNextCall(dead2);
-assertTrue(dead2(34, 11) == 34);
+  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(dead3(35, 12) == 35);
-assertTrue(dead3(35, 12) == 35);
+  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);
+%OptimizeFunctionOnNextCall(dead2);
 %OptimizeFunctionOnNextCall(dead3);
-assertTrue(dead3(35, 12) == 35);
+test();