test/mjsunit/regress/regress-seqstrsetchar-ex1.js

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// Flags: --allow-natives-syntax

// stubbed version of ToNumber
function ToNumber(x) {
  return 311;
}

// Reduced version of String.fromCharCode;
// does not actually do the same calculation but exhibits untagging bug.
function StringFromCharCode(code) {
  var n = %_ArgumentsLength();
  var one_byte = %NewString(n, true);
  var i;
  for (i = 0; i < n; i++) {
    var code = %_Arguments(i);
    if (!%_IsSmi(code)) code = ToNumber(code) & 0xffff;
    if (code > 0xff) break;
  }

  var two_byte = %NewString(n - i, false);
  for (var j = 0; i < n; i++, j++) {
    var code = %_Arguments(i);
    %_TwoByteSeqStringSetChar(j, code, two_byte);
  }
  return one_byte + two_byte;
}

StringFromCharCode(0xFFF, 0xFFF);
StringFromCharCode(0x7C, 0x7C);
%OptimizeFunctionOnNextCall(StringFromCharCode);
StringFromCharCode(0x7C, 0x7C);
StringFromCharCode(0xFFF, 0xFFF);