[LLVM][x86][Inline Asm] support for GCC style inline asm - Y<x> constraints

This patch is intended to enable the use of basic double letter constraints used in GCC extended inline asm {Yi Y2 Yz Y0 Ym Yt}.
Supersedes D35204
Clang counterpart: D36371

Differential Revision: https://reviews.llvm.org/D36369


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311644 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed