AMDGPU: Fix DAG divergence not reporting flat loads

Match behavior in DAG of r340343

llvm-svn: 341393
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 0028fe1..749a361 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -9206,10 +9206,10 @@
     }
     break;
     case ISD::LOAD: {
-      const LoadSDNode *L = dyn_cast<LoadSDNode>(N);
-      // FIXME: Also needs to handle flat.
-      if (L->getMemOperand()->getAddrSpace() == AMDGPUAS::PRIVATE_ADDRESS)
-        return true;
+      const LoadSDNode *L = cast<LoadSDNode>(N);
+      unsigned AS = L->getAddressSpace();
+      // A flat load may access private memory.
+      return AS == AMDGPUAS::PRIVATE_ADDRESS || AS == AMDGPUAS::FLAT_ADDRESS;
     } break;
     case ISD::CALLSEQ_END:
     return true;