[NVPTX] Added support for .f16x2 instructions.

This patch enables support for .f16x2 operations.

Added new register type Float16x2.
Added support for .f16x2 instructions.
Added handling of vectorized loads/stores of v2f16 values.

Differential Revision: https://reviews.llvm.org/D30057
Differential Revision: https://reviews.llvm.org/D30310

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296032 91177308-0d34-0410-b5e6-96231b3b80d8
15 files changed