[Driver] Don't pass -fobjc-rumtime= for non-ObjC input

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5613,7 +5613,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fexperimental_new_pass_manager,
                   options::OPT_fno_experimental_new_pass_manager);
 
-  ObjCRuntime Runtime = AddObjCRuntimeArgs(Args, CmdArgs, rewriteKind);
+  ObjCRuntime Runtime = AddObjCRuntimeArgs(Args, Inputs, CmdArgs, rewriteKind);
   RenderObjCOptions(TC, D, RawTriple, Args, Runtime, rewriteKind != RK_None,
                     Input, CmdArgs);
 
@@ -6257,6 +6257,7 @@ Clang::~Clang() {}
 ///
 /// Returns true if the runtime is non-fragile.
 ObjCRuntime Clang::AddObjCRuntimeArgs(const ArgList &args,
+                                      const InputInfoList &inputs,
                                       ArgStringList &cmdArgs,
                                       RewriteKind rewriteKind) const {
   // Look for the controlling runtime option.
@@ -6380,8 +6381,11 @@ ObjCRuntime Clang::AddObjCRuntimeArgs(const ArgList &args,
       runtime = ObjCRuntime(ObjCRuntime::GCC, VersionTuple());
   }
 
-  cmdArgs.push_back(
-      args.MakeArgString("-fobjc-runtime=" + runtime.getAsString()));
+  if (llvm::any_of(inputs, [](const InputInfo &input) {
+        return types::isObjC(input.getType());
+      }))
+    cmdArgs.push_back(
+        args.MakeArgString("-fobjc-runtime=" + runtime.getAsString()));
   return runtime;
 }
 

clang/lib/Driver/ToolChains/Clang.h

@@ -77,6 +77,7 @@ private:
   enum RewriteKind { RK_None, RK_Fragile, RK_NonFragile };
 
   ObjCRuntime AddObjCRuntimeArgs(const llvm::opt::ArgList &args,
+                                 const InputInfoList &inputs,
                                  llvm::opt::ArgStringList &cmdArgs,
                                  RewriteKind rewrite) const;
 

clang/test/Driver/darwin-objc-options.m

@@ -31,5 +31,12 @@
 // CHECK-CHECK-I386_IOS-NOT: -fobjc-dispatch-method
 // CHECK-CHECK-I386_IOS: darwin-objc-options
 
+/// Don't add -fobjc-runtime for non-ObjC input.
+// RUN: touch %t.c
+// RUN: %clang -target x86_64-apple-darwin -x objective-c -S -### %t.c 2>&1 | FileCheck --check-prefix=F %s
+// RUN: %clang -target x86_64-apple-darwin -S -### %t.c 2>&1 | FileCheck --check-prefix=NO_F %s
+// F: -fobjc-runtime=
+// NO_F-NOT: -fobjc-runtime=
+
 // Don't crash with an unexpected target triple.
 // RUN: %clang -target i386-apple-ios7 -S -### %s