[SYCL] Fix warnings on clang-based build (#3570)

Co-authored-by: Aaron Ballman <[email protected]>

Author: Pavel Chupin

clang/lib/Frontend/CompilerInvocation.cpp

@@ -521,9 +521,10 @@ static bool FixupInvocation(CompilerInvocation &Invocation,
 static unsigned getOptimizationLevel(ArgList &Args, InputKind IK,
                                      DiagnosticsEngine &Diags) {
   unsigned DefaultOpt = llvm::CodeGenOpt::None;
-  if ((IK.getLanguage() == Language::OpenCL ||
-       IK.getLanguage() == Language::OpenCLCXX) &&
-      !Args.hasArg(OPT_cl_opt_disable) || Args.hasArg(OPT_fsycl_is_device))
+  if (((IK.getLanguage() == Language::OpenCL ||
+        IK.getLanguage() == Language::OpenCLCXX) &&
+       !Args.hasArg(OPT_cl_opt_disable)) ||
+      Args.hasArg(OPT_fsycl_is_device))
     DefaultOpt = llvm::CodeGenOpt::Default;
 
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {

clang/lib/Sema/SemaSYCL.cpp

@@ -3192,7 +3192,9 @@ class SyclKernelIntFooterCreator : public SyclKernelFieldHandler {
 
 public:
   SyclKernelIntFooterCreator(Sema &S, SYCLIntegrationFooter &F)
-      : SyclKernelFieldHandler(S), Footer(F) {}
+      : SyclKernelFieldHandler(S), Footer(F) {
+    (void)Footer; // workaround for unused field warning
+  }
 };
 
 } // namespace

sycl/source/detail/os_util.cpp

@@ -218,7 +218,7 @@ std::string OSUtil::getDirName(const char *Path) {
   // Remove trailing directory separators
   Tmp.erase(Tmp.find_last_not_of("/\\") + 1, std::string::npos);
 
-  int pos = Tmp.find_last_of("/\\");
+  size_t pos = Tmp.find_last_of("/\\");
   if (pos != std::string::npos)
     return Tmp.substr(0, pos);