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[XLA] Avoid UB in absl::bitcast from Eigen::half.

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PiperOrigin-RevId: 219331320
This commit is contained in:
Michael Kuperstein 2018-10-30 11:09:02 -07:00 committed by TensorFlower Gardener
parent 507c566376
commit 6b8e08a932
1 changed files with 10 additions and 4 deletions
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14
tensorflow/compiler/xla/literal_comparison.cc
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@ -34,16 +34,22 @@ namespace xla {
namespace literal_comparison {
namespace {
// Since Eigen::half doesn't satisfy the absl::bit_cast contract, we need to be
// able to transparently access the raw 16-bit value contained within.
template <typename T>
T GetRawValue(T val) {
return val;
}
uint16 GetRawValue(Eigen::half val) { return val.x; }
// Helper function for comparing a floating point type, FloatT, bitwise equal
// between the left-hand-side and right-hand-side, by bit-casting to UnsignedT
// -- on miscompare, a nice error message is given in the AssertionFailure.
template <typename FloatT, typename UnsignedT>
Status CompareFloatsBitwiseEqual(FloatT lhs, FloatT rhs,
absl::Span<const int64> multi_index) {
// TODO(b/118627822): These are unsafe bit_casts because Eigen::Half is not
// trivially copyable.
auto ulhs = absl::bit_cast<UnsignedT>(lhs);
auto urhs = absl::bit_cast<UnsignedT>(rhs);
auto ulhs = absl::bit_cast<UnsignedT>(GetRawValue(lhs));
auto urhs = absl::bit_cast<UnsignedT>(GetRawValue(rhs));
auto lhs_double = static_cast<double>(lhs);
auto rhs_double = static_cast<double>(rhs);
if (ulhs != urhs) {