diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1211,9 +1211,6 @@
   // FIXME: This stuff needs to go into the Compilation, not the driver.
   bool CCCPrintPhases;
 
-  // Silence driver warnings if requested
-  Diags.setIgnoreAllWarnings(Args.hasArg(options::OPT_w));
-
   // -canonical-prefixes, -no-canonical-prefixes are used very early in main.
   Args.ClaimAllArgs(options::OPT_canonical_prefixes);
   Args.ClaimAllArgs(options::OPT_no_canonical_prefixes);
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -3797,8 +3797,10 @@
   }
 
   // Configure the diagnostics.
+  std::unique_ptr<DiagnosticOptions> DiagOpts = CreateAndPopulateDiagOpts(
+      llvm::makeArrayRef(command_line_args, num_command_line_args));
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
-      CompilerInstance::createDiagnostics(new DiagnosticOptions));
+      CompilerInstance::createDiagnostics(DiagOpts.release()));
 
   if (options & CXTranslationUnit_KeepGoing)
     Diags->setFatalsAsError(true);