R600/SI: Add a stub GCNTargetMachine

This is equivalent to the AMDGPUTargetMachine now, but it is the
starting point for separating R600 and GCN functionality into separate
targets.

It is recommened that users start using the gcn triple for GCN-based
GPUs, because using the r600 triple for these GPUs will be deprecated in
the future.

llvm-svn: 225277
diff --git a/llvm/test/CodeGen/R600/shl_add_ptr.ll b/llvm/test/CodeGen/R600/shl_add_ptr.ll
index fdb3d39..cef48e2 100644
--- a/llvm/test/CodeGen/R600/shl_add_ptr.ll
+++ b/llvm/test/CodeGen/R600/shl_add_ptr.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=r600 -mcpu=bonaire -verify-machineinstrs -mattr=+load-store-opt -enable-misched < %s | FileCheck -check-prefix=SI %s
+; RUN: llc -march=amdgcn -mcpu=bonaire -verify-machineinstrs -mattr=+load-store-opt -enable-misched < %s | FileCheck -check-prefix=SI %s
 
 ; Test that doing a shift of a pointer with a constant add will be
 ; folded into the constant offset addressing mode even if the add has