[SYCL][NFC] Fix warnings reported by Clang (#3050)

Author: Alexander Batashev

sycl/include/CL/sycl/INTEL/online_compiler.hpp

@@ -94,7 +94,7 @@ template <source_language Lang> class online_compiler {
   // TODO: the initial version generates the generic code (SKL now), need
   // to do additional device::info calls to determine the device by it's
   // features.
-  online_compiler(const sycl::device &dev)
+  online_compiler(const sycl::device &)
       : OutputFormat(compiled_code_format::spir_v), OutputFormatVersion({0, 0}),
         DeviceType(sycl::info::device_type::all), DeviceArch(device_arch::any),
         Is64Bit(true), DeviceStepping("") {}

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -5525,6 +5525,7 @@ pi_result piPluginInit(pi_plugin *PluginInit) {
 // It can include all the jobs to tear down resources before
 // the plugin is unloaded from memory.
 pi_result piTearDown(void *PluginParameter) {
+  (void)PluginParameter;
   // reclaim pi_platform objects here since we don't have piPlatformRelease.
   for (pi_platform &Platform : *PiPlatformsCache) {
     delete Platform;

sycl/plugins/opencl/pi_opencl.cpp

@@ -1181,7 +1181,10 @@ pi_result piextProgramGetNativeHandle(pi_program program,
 // This API is called by Sycl RT to notify the end of the plugin lifetime.
 // TODO: add a global variable lifetime management code here (see
 // pi_level_zero.cpp for reference) Currently this is just a NOOP.
-pi_result piTearDown(void *PluginParameter) { return PI_SUCCESS; }
+pi_result piTearDown(void *PluginParameter) {
+  (void)PluginParameter;
+  return PI_SUCCESS;
+}
 
 pi_result piPluginInit(pi_plugin *PluginInit) {
   int CompareVersions = strcmp(PluginInit->PiVersion, SupportedVersion);

sycl/source/detail/device_info.hpp

@@ -279,9 +279,8 @@ static bool is_sycl_partition_property(info::partition_property PP) {
   case info::partition_property::partition_by_counts:
   case info::partition_property::partition_by_affinity_domain:
     return true;
-  default:
-    return false;
   }
+  return false;
 }
 
 // Specialization for partition properties, variable OpenCL return size

sycl/source/detail/plugin_printers.hpp

@@ -128,7 +128,7 @@ void printArgs(Arg0 arg0, Args... args) {
 }
 
 template <typename T> struct printOut {
-  printOut(T val) {}
+  printOut(T) {}
 }; // Do nothing
 
 template <> struct printOut<PiEvent *> {