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/build_vector.ll b/llvm/test/CodeGen/AMDGPU/build_vector.ll
index 65eacf5..0a5774c 100644
--- a/llvm/test/CodeGen/AMDGPU/build_vector.ll
+++ b/llvm/test/CodeGen/AMDGPU/build_vector.ll
@@ -1,6 +1,6 @@
 ; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck %s --check-prefix=R600
-; RUN: llc < %s -march=amdgcn -mcpu=SI -verify-machineinstrs | FileCheck %s --check-prefix=SI
-; RUN: llc < %s -march=amdgcn -mcpu=tonga -verify-machineinstrs | FileCheck %s --check-prefix=SI
+; RUN: llc < %s -march=amdgcn -verify-machineinstrs | FileCheck %s --check-prefix=SI
+; RUN: llc < %s -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -verify-machineinstrs | FileCheck %s --check-prefix=SI
 
 ; R600: {{^}}build_vector2:
 ; R600: MOV