tBfar is bl, which clobbers LR.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78370 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index 782765a..2f74133 100644
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -1221,7 +1221,8 @@
 ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br) {
   MachineInstr *MI = Br.MI;
   MachineBasicBlock *MBB = MI->getParent();
-  assert(isThumb && !isThumb2 && "Expected a Thumb1 function!");
+  if (!isThumb1)
+    llvm_unreachable("FixUpUnconditionalBr is Thumb1 only!");
 
   // Use BL to implement far jump.
   Br.MaxDisp = (1 << 21) * 2;