Convert assert(0) to llvm_unreachable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149816 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocPBQP.cpp b/lib/CodeGen/RegAllocPBQP.cpp
index f8b0b9f..4715263 100644
--- a/lib/CodeGen/RegAllocPBQP.cpp
+++ b/lib/CodeGen/RegAllocPBQP.cpp
@@ -529,7 +529,7 @@
       // We need another round if spill intervals were added.
       anotherRoundNeeded |= !LRE.empty();
     } else {
-      assert(false && "Unknown allocation option.");
+      llvm_unreachable("Unknown allocation option.");
     }
   }