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/mad_int24.ll b/llvm/test/CodeGen/AMDGPU/mad_int24.ll
index f177608..f149ea0 100644
--- a/llvm/test/CodeGen/AMDGPU/mad_int24.ll
+++ b/llvm/test/CodeGen/AMDGPU/mad_int24.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -march=amdgcn -verify-machineinstrs | FileCheck %s --check-prefix=SI --check-prefix=FUNC
-; RUN: llc < %s -march=amdgcn -mcpu=tonga -verify-machineinstrs | FileCheck %s --check-prefix=SI --check-prefix=FUNC
+; RUN: llc < %s -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -verify-machineinstrs | FileCheck %s --check-prefix=SI --check-prefix=FUNC
 ; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck %s --check-prefix=EG --check-prefix=FUNC
 ; RUN: llc < %s -march=r600 -mcpu=cayman | FileCheck %s --check-prefix=CM --check-prefix=FUNC