message: [XLA/GPU] Comment polishing.
diff: @@ -166,14 +166,14 @@ bool ConcatIsEffectivelyElementwise(
  // Limit our supported cases to 1 dimensional slices.
  return false;
  }
  - absl::c_sort(users, [](const HloInstruction* a, const HloInstruction* b) {
  - return a->slice_starts().at(0) < b->slice_starts().at(0);
  - });
  // Verify that each operand to the concat is reversed by a slice.
  if (users.size() != concat.operand_count() ||
  concat.operand_count() != concat.unique_operands().size()) {
  return false;
  }
  + absl::c_sort(users, [](const HloInstruction* a, const HloInstruction* b) {
  + return a->slice_starts().at(0) < b->slice_starts().at(0);
  + });
  int64 prev_limit = 0;
  for (int64 i = 0; i < users.size(); ++i) {
  const HloInstruction* u = users[i];
  @@ -185,7 +185,10 @@ bool ConcatIsEffectivelyElementwise(
  prev_limit = u->slice_limits().at(0);
  }
  - // If we have seen other concats, make sure they are identical.
  + // If we have seen other concats, make sure they are identical. Multiple
  + // concats exist because horizontal fusion inserts one concat for each output
  + // of the fusion candidates. Check all concats and operand ids are the same
  + // to make sure that the compute iteration space is the same.
  int64 operand_idx = concat.operand_index(&operand);
  *slice_to_recover_opnd = users.at(operand_idx);
  if (prev_concat_opnd_idx->first == nullptr) {
  @@ -207,8 +210,10 @@ bool ConcatIsEffectivelyElementwise(
  }
  // Returns whether we can prove the transitive uses of `param` are in effect
  -// elementwise. In other words, we prove that the transitive use closure will
  +// elementwise. In other words, we prove that the "transitive use closure" will
  // all be computed in the same iteration space without any reorder of elements.
  +// In addition, we check that the "transitive use closure" includes the output
  +// in the `root_tuple`.
  // Theoretically, We can prove more patterns but our primary use case is
  // SliceInputFusion.
  bool AreTransitiveUsesEffectivelyElementwise(const HloInstruction* param,
  