src/v8/test/mjsunit/nans.js

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

// Helper to determine endian - returns true on little endian platforms
function isLittleEndian() {
  return ((new Uint32Array((new Uint8Array([4,3,2,1])).buffer))[0])
           == 0x01020304;
}

// Test that both kinds of NaNs (signaling or quiet) do not signal

function TestAllModes(f) {
  f(); // Runtime
  f(); // IC
  f(); // IC second time
  %OptimizeFunctionOnNextCall(f);
  f(); // hydrogen
}

function TestDoubleSignalingNan() {
  // NaN with signal bit set
  function f() {
    if(isLittleEndian()) {
      var bytes = new Uint32Array([1, 0x7FF00000]);
    } else {
      var bytes = new Uint32Array([0x7FF00000, 1]);
    }
    var doubles = new Float64Array(bytes.buffer);
    assertTrue(isNaN(doubles[0]));
    assertTrue(isNaN(doubles[0]*2.0));
    assertTrue(isNaN(doubles[0] + 0.5));
  }

  TestAllModes(f);
}

TestDoubleSignalingNan();

function TestDoubleQuietNan() {
  // NaN with signal bit cleared
  function f() {
    if(isLittleEndian()) {
      var bytes = new Uint32Array([0, 0x7FF80000]);
    } else {
      var bytes = new Uint32Array([0x7FF80000, 0]);
    }
    var doubles = new Float64Array(bytes.buffer);
    assertTrue(isNaN(doubles[0]));
    assertTrue(isNaN(doubles[0]*2.0));
    assertTrue(isNaN(doubles[0] + 0.5));
  }

  TestAllModes(f);
}

TestDoubleQuietNan();

function TestFloatSignalingNan() {
  // NaN with signal bit set
  function f() {
    var bytes = new Uint32Array([0x7F800001]);
    var floats = new Float32Array(bytes.buffer);
    assertTrue(isNaN(floats[0]));
    assertTrue(isNaN(floats[0]*2.0));
    assertTrue(isNaN(floats[0] + 0.5));
  }

  TestAllModes(f);
}

TestFloatSignalingNan();

function TestFloatQuietNan() {
  // NaN with signal bit cleared
  function f() {
    var bytes = new Uint32Array([0x7FC00000]);
    var floats = new Float32Array(bytes.buffer);
    assertTrue(isNaN(floats[0]));
    assertTrue(isNaN(floats[0]*2.0));
    assertTrue(isNaN(floats[0] + 0.5));
  }

  TestAllModes(f);
}

TestFloatQuietNan();