[XLA] First step in adding Literal slice classes, to improve interface safety

and prepare for enabling more efficient interfacing from Tensor to Literal to
reduce host to device latency.

More specically:
* Introducing a new LiteralBase abstract base class that contains all immutable
methods of from the old Literal class.

* Introducing a subclass LiteralSlice to replace original LiteralView class.
LiteralSlice class is read-only and does not own Shape nor any buffer through
the Pieces. Change a number of callers to use LiteralSlice directly.

* Change Literal class to explicitly own the underlying Shape as well as owning
the underlying buffer via Piece.

* Conversion from Literal to LiteralSlice is now done via an implicit
conversion constructor instead of inheritance.

* Decouple ShapeTree from Literal classes.

* Use copy-and-swap for assignment constructors.

* Other minor cleanups.

PiperOrigin-RevId: 196016576

1 files changed, 2 insertions, 2 deletions

diff --git a/tensorflow/compiler/xla/service/algebraic_simplifier.cc b/tensorflow/compiler/xla/service/algebraic_simplifier.cc
index 4ec79a0244..3ce80bba17 100644
--- a/tensorflow/compiler/xla/service/algebraic_simplifier.cc
+++ b/tensorflow/compiler/xla/service/algebraic_simplifier.cc
@@ -501,13 +501,13 @@ Status AlgebraicSimplifierVisitor::HandleConcatenate(
 }
 
 static HloInstruction* BuildTupleConstant(HloComputation* computation,
-                                          const Literal& literal) {
+                                          const LiteralSlice& literal) {
   if (ShapeUtil::IsTuple(literal.shape())) {
     std::vector<HloInstruction*> elems;
     elems.reserve(ShapeUtil::TupleElementCount(literal.shape()));
     for (int i = 0; i < ShapeUtil::TupleElementCount(literal.shape()); ++i) {
       elems.push_back(
-          BuildTupleConstant(computation, LiteralView::Create(literal, {i})));
+          BuildTupleConstant(computation, LiteralSlice(literal, {i})));
     }
     return computation->AddInstruction(HloInstruction::CreateTuple(elems));
   } else {