Enable FeatureFlatForGlobal on Volcanic Islands

This switches to the workaround that HSA defaults to
for the mesa path.

This should be applied to the 4.0 branch.

Patch by Vedran Miletić <vedran@miletic.net>

llvm-svn: 292982
diff --git a/llvm/test/CodeGen/AMDGPU/add.i16.ll b/llvm/test/CodeGen/AMDGPU/add.i16.ll
index a41d307..6c5cdd3 100644
--- a/llvm/test/CodeGen/AMDGPU/add.i16.ll
+++ b/llvm/test/CodeGen/AMDGPU/add.i16.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=VI -check-prefix=GCN %s
+; RUN: llc -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=VI -check-prefix=GCN %s
 
 ; FIXME: Need to handle non-uniform case for function below (load without gep).
 ; GCN-LABEL: {{^}}v_test_add_i16: