Index: lib/CodeGen/RegAllocGreedy.cpp
===================================================================
--- lib/CodeGen/RegAllocGreedy.cpp
+++ lib/CodeGen/RegAllocGreedy.cpp
@@ -726,7 +726,7 @@
   if (Matrix->checkInterference(VirtReg, PhysReg) > LiveRegMatrix::IK_VirtReg)
     return false;
 
-  bool IsLocal = LIS->intervalIsInOneMBB(VirtReg);
+  bool IsLocal = VirtReg.empty() || LIS->intervalIsInOneMBB(VirtReg);
 
   // Find VirtReg's cascade number. This will be unassigned if VirtReg was never
   // involved in an eviction before. If a cascade number was assigned, deny
Index: test/CodeGen/AMDGPU/branch-on-undef.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AMDGPU/branch-on-undef.ll
@@ -0,0 +1,14 @@
+; RUN: llc -march=amdgcn -verify-machineinstrs < %s
+
+define void @undef_br(i32 addrspace(1)* %ptr) nounwind {
+entry:
+  br i1 undef, label %exit, label %bb
+
+bb:
+  store volatile i32 0, i32 addrspace(1)* %ptr
+  br label %exit
+
+exit:
+  ret void
+}
+