AMDGPU/R600: Add PatFrags for selecting the correct vtx id for loads

This moves of the r600 logic out of isGlobalLoad() and into the
TableGen files.

Differential Revision: http://reviews.llvm.org/D21710

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274527 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed