Convert assert(0) to llvm_unreachable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149816 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/RegAllocPBQP.cpp

@@ -529,7 +529,7 @@ bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAProblem &problem,
       // We need another round if spill intervals were added.
       anotherRoundNeeded |= !LRE.empty();
     } else {
-      assert(false && "Unknown allocation option.");
+      llvm_unreachable("Unknown allocation option.");
     }
   }