diff --git a/lib/Frontend/ASTConsumers.cpp b/lib/Frontend/ASTConsumers.cpp
index 6412727..70baf74 100644
--- a/lib/Frontend/ASTConsumers.cpp
+++ b/lib/Frontend/ASTConsumers.cpp
@@ -286,7 +286,7 @@
   }
 
   default:
-    assert(0 && "a decl that inherits DeclContext isn't handled");
+    llvm_unreachable("a decl that inherits DeclContext isn't handled");
   }
 
   Out << "\n";
@@ -392,7 +392,7 @@
     }
     default:
       Out << "DeclKind: " << DK << '"' << *I << "\"\n";
-      assert(0 && "decl unhandled");
+      llvm_unreachable("decl unhandled");
     }
   }
 }
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index e699261..03d06e6 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1164,7 +1164,7 @@
   if (const Arg *A = Args.getLastArg(OPT_Action_Group)) {
     switch (A->getOption().getID()) {
     default:
-      assert(0 && "Invalid option in group!");
+      llvm_unreachable("Invalid option in group!");
     case OPT_ast_dump:
       Opts.ProgramAction = frontend::ASTDump; break;
     case OPT_ast_dump_xml:
@@ -1457,7 +1457,7 @@
     case IK_None:
     case IK_AST:
     case IK_LLVM_IR:
-      assert(0 && "Invalid input kind!");
+      llvm_unreachable("Invalid input kind!");
     case IK_OpenCL:
       LangStd = LangStandard::lang_opencl;
       break;
diff --git a/lib/Frontend/TextDiagnosticBuffer.cpp b/lib/Frontend/TextDiagnosticBuffer.cpp
index 069c86d..c03ac54 100644
--- a/lib/Frontend/TextDiagnosticBuffer.cpp
+++ b/lib/Frontend/TextDiagnosticBuffer.cpp
@@ -26,7 +26,8 @@
   llvm::SmallString<100> Buf;
   Info.FormatDiagnostic(Buf);
   switch (Level) {
-  default: assert(0 && "Diagnostic not handled during diagnostic buffering!");
+  default: llvm_unreachable(
+                         "Diagnostic not handled during diagnostic buffering!");
   case Diagnostic::Note:
     Notes.push_back(std::make_pair(Info.getLocation(), Buf.str()));
     break;
diff --git a/lib/Frontend/TextDiagnosticPrinter.cpp b/lib/Frontend/TextDiagnosticPrinter.cpp
index 4fc6949..762a7c5 100644
--- a/lib/Frontend/TextDiagnosticPrinter.cpp
+++ b/lib/Frontend/TextDiagnosticPrinter.cpp
@@ -1083,7 +1083,7 @@
   if (DiagOpts->ShowColors) {
     // Print diagnostic category in bold and color
     switch (Level) {
-    case Diagnostic::Ignored: assert(0 && "Invalid diagnostic type");
+    case Diagnostic::Ignored: llvm_unreachable("Invalid diagnostic type");
     case Diagnostic::Note:    OS.changeColor(noteColor, true); break;
     case Diagnostic::Warning: OS.changeColor(warningColor, true); break;
     case Diagnostic::Error:   OS.changeColor(errorColor, true); break;
@@ -1092,7 +1092,7 @@
   }
 
   switch (Level) {
-  case Diagnostic::Ignored: assert(0 && "Invalid diagnostic type");
+  case Diagnostic::Ignored: llvm_unreachable("Invalid diagnostic type");
   case Diagnostic::Note:    OS << "note: "; break;
   case Diagnostic::Warning: OS << "warning: "; break;
   case Diagnostic::Error:   OS << "error: "; break;