v8/test/mjsunit/array-literal-feedback.js

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// Flags: --allow-natives-syntax --smi-only-arrays --expose-gc
// Flags: --noalways-opt

// Test element kind of objects.
// Since --smi-only-arrays affects builtins, its default setting at compile
// time sticks if built with snapshot.  If --smi-only-arrays is deactivated
// by default, only a no-snapshot build actually has smi-only arrays enabled
// in this test case.  Depending on whether smi-only arrays are actually
// enabled, this test takes the appropriate code path to check smi-only arrays.

// Reset the GC stress mode to be off. Needed because AllocationMementos only
// live for one gc, so a gc that happens in certain fragile areas of the test
// can break assumptions.
%SetFlags("--gc-interval=-1")

// support_smi_only_arrays = %HasFastSmiElements(new Array(1,2,3,4,5,6,7,8));
support_smi_only_arrays = true;

if (support_smi_only_arrays) {
  print("Tests include smi-only arrays.");
} else {
  print("Tests do NOT include smi-only arrays.");
}

var elements_kind = {
  fast_smi_only            :  'fast smi only elements',
  fast                     :  'fast elements',
  fast_double              :  'fast double elements',
  dictionary               :  'dictionary elements',
  external_byte            :  'external byte elements',
  external_unsigned_byte   :  'external unsigned byte elements',
  external_short           :  'external short elements',
  external_unsigned_short  :  'external unsigned short elements',
  external_int             :  'external int elements',
  external_unsigned_int    :  'external unsigned int elements',
  external_float           :  'external float elements',
  external_double          :  'external double elements',
  external_pixel           :  'external pixel elements'
}

function getKind(obj) {
  if (%HasFastSmiElements(obj)) return elements_kind.fast_smi_only;
  if (%HasFastObjectElements(obj)) return elements_kind.fast;
  if (%HasFastDoubleElements(obj)) return elements_kind.fast_double;
  if (%HasDictionaryElements(obj)) return elements_kind.dictionary;
}

function isHoley(obj) {
  if (%HasFastHoleyElements(obj)) return true;
  return false;
}

function assertKind(expected, obj, name_opt) {
  if (!support_smi_only_arrays &&
      expected == elements_kind.fast_smi_only) {
    expected = elements_kind.fast;
  }
  assertEquals(expected, getKind(obj), name_opt);
}

if (support_smi_only_arrays) {

  function get_literal(x) {
    var literal = [1, 2, x];
    return literal;
  }

  get_literal(3);
  // It's important to store a from before we crankshaft get_literal, because
  // mementos won't be created from crankshafted code at all.
  a = get_literal(3);
  %OptimizeFunctionOnNextCall(get_literal);
  get_literal(3);
  assertOptimized(get_literal);
  assertTrue(%HasFastSmiElements(a));
  // a has a memento so the transition caused by the store will affect the
  // boilerplate.
  a[0] = 3.5;

  // We should have transitioned the boilerplate array to double, and
  // crankshafted code should de-opt on the unexpected elements kind
  b = get_literal(3);
  assertTrue(%HasFastDoubleElements(b));
  assertEquals([1, 2, 3], b);
  assertUnoptimized(get_literal);

  // Optimize again
  get_literal(3);
  %OptimizeFunctionOnNextCall(get_literal);
  b = get_literal(3);
  assertTrue(%HasFastDoubleElements(b));
  assertOptimized(get_literal);


  // Test: make sure allocation site information is updated through a
  // transition from SMI->DOUBLE->FAST
  (function() {
    function bar(a, b, c) {
      return [a, b, c];
    }

    a = bar(1, 2, 3);
    a[0] = 3.5;
    a[1] = 'hi';
    b = bar(1, 2, 3);
    assertKind(elements_kind.fast, b);
  })();
}