AMDGPU: Restore AMDGPU prefixed rsq intrinsic for now

Also move into backend intrinsics to discourage use of the old name.

llvm-svn: 258783
diff --git a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index 4510246..92deda1 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -801,10 +801,11 @@
                                   AMDGPU::T0_Z, VT);
 
     // FIXME: Should be renamed to r600 prefix
-    case Intrinsic::AMDGPU_rsq_clamped:
+    case AMDGPUIntrinsic::AMDGPU_rsq_clamped:
       return DAG.getNode(AMDGPUISD::RSQ_CLAMPED, DL, VT, Op.getOperand(1));
 
     case Intrinsic::r600_rsq:
+    case AMDGPUIntrinsic::AMDGPU_rsq: // Legacy name
       // XXX - I'm assuming SI's RSQ_LEGACY matches R600's behavior.
       return DAG.getNode(AMDGPUISD::RSQ_LEGACY, DL, VT, Op.getOperand(1));
     }