v8/test/mjsunit/compiler/dead-string-char-code-at.js

// Copyright 2013 the V8 project authors. All rights reserved.
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// Flags: --allow-natives-syntax

var S1 = "string1";
var S2 = "@@string2";

function dead1(a, b) {
    var x = %_StringCharCodeAt(a, 4);
    return a; // x is dead code
}

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 = 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
}

function test() {
  var S3 = S1 + S2;

  assertEquals(S1, dead1(S1, S2));
  assertEquals(S1, dead2(S1, S2));
  assertEquals("11", dead3(S1, S2));

  assertEquals(S2, dead1(S2, 677));
  assertEquals(S2, dead2(S2, S3));
  assertEquals("11", dead3(S2, S3));

  assertEquals(S3, dead1(S3, 399));
  assertEquals(S3, dead2(S3, "false"));
  assertEquals("12", dead3(0, 32));

  assertEquals(S3, dead1(S3, 0));
  assertEquals(S3, dead2(S3, S1));
  assertEquals("11", dead3(S3, 0));

  assertEquals("true", dead1("true", 0));
  assertEquals("true", dead2("true", S3));
  assertEquals("11", dead3("true", 0));
}

test();
test();
%OptimizeFunctionOnNextCall(dead1);
%OptimizeFunctionOnNextCall(dead2);
%OptimizeFunctionOnNextCall(dead3);
test();