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/fsqrt.f64.ll b/llvm/test/CodeGen/AMDGPU/fsqrt.f64.ll
index ce0881c..ed04043 100644
--- a/llvm/test/CodeGen/AMDGPU/fsqrt.f64.ll
+++ b/llvm/test/CodeGen/AMDGPU/fsqrt.f64.ll
@@ -1,5 +1,5 @@
 ; RUN: llc -march=amdgcn -mcpu=tahiti -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=FUNC %s
-; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN -check-prefix=FUNC %s
 
 ; FUNC-LABEL: {{^}}v_safe_fsqrt_f64:
 ; GCN: v_sqrt_f64_e32 {{v\[[0-9]+:[0-9]+\], v\[[0-9]+:[0-9]+\]}}