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/load-constant-f64.ll b/llvm/test/CodeGen/AMDGPU/load-constant-f64.ll
index f94a378..1b42a9e 100644
--- a/llvm/test/CodeGen/AMDGPU/load-constant-f64.ll
+++ b/llvm/test/CodeGen/AMDGPU/load-constant-f64.ll
@@ -1,6 +1,6 @@
 ; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=GCN-NOHSA -check-prefix=FUNC %s
 ; RUN: llc -mtriple=amdgcn-amdhsa -mcpu=kaveri -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=GCN-HSA -check-prefix=FUNC %s
-; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=GCN-NOHSA -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=GCN-NOHSA -check-prefix=FUNC %s
 
 ; FUNC-LABEL: {{^}}constant_load_f64:
 ; GCN: s_load_dwordx2 s[{{[0-9]+:[0-9]+}}]