v8/test/mjsunit/constant-folding.js

// Copyright 2009 the V8 project authors. All rights reserved.
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// Test operations that involve one or more constants.
// The code generator now handles compile-time constants specially.
// Test the code generated when operands are known at compile time

// Test count operations involving constants
function test_count() {
  var x = "foo";
  var y = "3";

  x += x++;  // ++ and -- apply ToNumber to their operand, even for postfix.
  assertEquals(x, "fooNaN", "fooNaN test");
  x = "luft";
  x += ++x;
  assertEquals(x, "luftNaN", "luftNaN test");

  assertTrue(y++ === 3, "y++ === 3, where y = \"3\"");
  y = 3;
  assertEquals(y++, 3, "y++ == 3, where y = 3");
  y = "7.1";
  assertTrue(y++ === 7.1, "y++ === 7.1, where y = \"7.1\"");
  var z = y = x = "9";
  assertEquals( z++ + (++y) + x++, 28, "z++ + (++y) + x++ == 28");
  z = y = x = 13;
  assertEquals( z++ + (++y) + x++, 40, "z++ + (++y) + x++ == 40");
  z = y = x = -5.5;
  assertEquals( z++ + (++y) + x++, -15.5, "z++ + (++y) + x++ == -15.5");

  assertEquals(y, -4.5);
  z = y;
  z++;
  assertEquals(y, -4.5);
  z = y;
  y++;
  assertEquals(z, -4.5);

  y = 20;
  z = y;
  z++;
  assertEquals(y, 20);
  z = y;
  y++;
  assertEquals(z, 20);

  const w = 30;
  assertEquals(w++, 30);
  assertEquals(++w, 31);
  assertEquals(++w, 31);
}

test_count();

// Test comparison operations that involve one or two constant smis.

function test() {
  var i = 5;
  var j = 3;

  assertTrue( j < i );
  i = 5; j = 3;
  assertTrue( j <= i );
  i = 5; j = 3;
  assertTrue( i > j );
  i = 5; j = 3;
  assertTrue( i >= j );
  i = 5; j = 3;
  assertTrue( i != j );
  i = 5; j = 3;
  assertTrue( i == i );
  i = 5; j = 3;
  assertFalse( i < j );
  i = 5; j = 3;
  assertFalse( i <= j );
  i = 5; j = 3;
  assertFalse( j > i );
  i = 5; j = 3;
  assertFalse(j >= i );
  i = 5; j = 3;
  assertFalse( j == i);
  i = 5; j = 3;
  assertFalse( i != i);

  i = 10 * 10;
  while ( i < 107 ) {
    ++i;
  }
  j = 21;

  assertTrue( j < i );
  j = 21;
  assertTrue( j <= i );
  j = 21;
  assertTrue( i > j );
  j = 21;
  assertTrue( i >= j );
  j = 21;
  assertTrue( i != j );
  j = 21;
  assertTrue( i == i );
  j = 21;
  assertFalse( i < j );
  j = 21;
  assertFalse( i <= j );
  j = 21;
  assertFalse( j > i );
  j = 21;
  assertFalse(j >= i );
  j = 21;
  assertFalse( j == i);
  j = 21;
  assertFalse( i != i);
  j = 21;
  assertTrue( j == j );
  j = 21;
  assertFalse( j != j );

  assertTrue( 100 > 99 );
  assertTrue( 101 >= 90 );
  assertTrue( 11111 > -234 );
  assertTrue( -888 <= -20 );

  while ( 234 > 456 ) {
    i = i + 1;
  }

  switch(3) {
    case 5:
      assertUnreachable();
      break;
    case 3:
      j = 13;
    default:
      i = 2;
    case 7:
      j = 17;
      break;
    case 9:
      j = 19;
      assertUnreachable();
      break;
  }
  assertEquals(17, j, "switch with constant value");
}


function TrueToString() {
  return true.toString();
}


function FalseToString() {
  return false.toString();
}


function BoolTest() {
  assertEquals("true", TrueToString());
  assertEquals("true", TrueToString());
  assertEquals("true", TrueToString());
  assertEquals("false", FalseToString());
  assertEquals("false", FalseToString());
  assertEquals("false", FalseToString());
  Boolean.prototype.toString = function() { return "foo"; }
  assertEquals("foo", TrueToString());
  assertEquals("foo", FalseToString());
}


// Some tests of shifts that get into the corners in terms of coverage.
// We generate different code for the case where the operand is a constant.
function ShiftTest() {
  var x = 123;
  assertEquals(x, x >> 0);
  assertEquals(x, x << 0);
  assertEquals(x, x >>> 0);
  assertEquals(61, x >> 1);
  assertEquals(246, x << 1);
  assertEquals(61, x >>> 1);
  x = -123;
  assertEquals(x, x >> 0);
  assertEquals(x, x << 0);
  assertEquals(0x10000 * 0x10000 + x, x >>> 0);
  assertEquals(-62, x >> 1);
  assertEquals(-246, x << 1);
  assertEquals(0x10000 * 0x8000 - 62, x >>> 1);
  // Answer is non-Smi so the subtraction is not folded in the code
  // generator.
  assertEquals(-0x40000001, -0x3fffffff - 2);

  x = 123;
  assertEquals(0, x & 0);

  // Answer is non-smi and lhs of << is a temporary heap number that we can
  // overwrite.
  x = 123.0001;
  assertEquals(1073741824, (x * x) << 30);
  x = 123;
  // Answer is non-smi and lhs of << is a temporary heap number that we think
  // we can overwrite (but we can't because it's a Smi).
  assertEquals(1073741824, (x * x) << 30);
}


test();
BoolTest();
ShiftTest();