v8/test/mjsunit/smi-mul-const.js

// Copyright 2014 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
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//
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// Flags: --allow-natives-syntax --opt --noalways-opt

function check(func, input, expected) {
  %PrepareFunctionForOptimization(func);
  func(-1);
  func(-1);
  %OptimizeFunctionOnNextCall(func);
  assertEquals(expected, func(input));
  assertOptimized(func);
}

function mul_by_neg_1(a) { return a * -1; }
function mul_by_0(a) {  return a * 0; }
function mul_by_1(a) { return a * 1; }
function mul_by_2(a) { return a * 2; }

check(mul_by_neg_1, 2, -2);
check(mul_by_0, 2, 0);
check(mul_by_1, 2, 2);
check(mul_by_2, 2, 4);

function limit_range(a) {
  // Limit the range of 'a' to enable no-overflow optimizations.
  return Math.max(Math.min(a | 0, 10), -10);
}
%EnsureFeedbackVectorForFunction(limit_range);

function mul_by_neg_127(a) { return limit_range(a) * -127; }
function mul_by_neg_128(a) { return limit_range(a) * -128; }
function mul_by_neg_129(a) { return limit_range(a) * -129; }
function mul_by_1023(a) { return limit_range(a) * 1023; }
function mul_by_1024(a) { return limit_range(a) * 1024; }
function mul_by_1025(a) { return limit_range(a) * 1025; }

check(mul_by_neg_127, 2, -254);
check(mul_by_neg_128, 2, -256);
check(mul_by_neg_129, 2, -258);
check(mul_by_1023, 2, 2046);
check(mul_by_1024, 2, 2048);
check(mul_by_1025, 2, 2050);

// Deopt on minus zero.
assertEquals(-0, mul_by_neg_128(0));
assertUnoptimized(mul_by_neg_128);
assertEquals(-0, mul_by_2(-0));
assertUnoptimized(mul_by_2);

// Deopt on overflow.

// -2^30 is in Smi range on most configurations, +2^30 is not.
var two_30 = 1 << 30;
assertEquals(two_30, mul_by_neg_1(-two_30));

// For good measure, check that overflowing int32 range (or Smi range
// without pointer compression) works too.
var two_31 = two_30 * 2;
assertEquals(two_31, mul_by_neg_1(-two_31));

// One of the two situations deoptimized the code.
assertUnoptimized(mul_by_neg_1);