[SYCL] Avoid unnecessary kernel copies

sycl/include/sycl/detail/cg_types.hpp

@@ -167,7 +167,8 @@ class HostKernel : public HostKernelBase {
   KernelType MKernel;
 
 public:
-  HostKernel(KernelType Kernel) : MKernel(Kernel) {}
+  HostKernel(const KernelType &Kernel) : MKernel(Kernel) {}
+  HostKernel(KernelType &&Kernel) : MKernel(std::move(Kernel)) {}
 
   char *getPtr() override { return reinterpret_cast<char *>(&MKernel); }
 

sycl/include/sycl/handler.hpp

@@ -715,17 +715,18 @@ class __SYCL_EXPORT handler {
   /// \param KernelFunc is a SYCL kernel function
   /// \param ParamDescs is the vector of kernel parameter descriptors.
   template <typename KernelName, typename KernelType, int Dims,
-            typename LambdaArgType>
-  void StoreLambda(KernelType KernelFunc) {
+  typename LambdaArgType, typename KernelTypeUniversalRef>
+  void StoreLambda(KernelTypeUniversalRef &&KernelFunc) {
     constexpr bool IsCallableWithKernelHandler =
         detail::KernelLambdaHasKernelHandlerArgT<KernelType,
                                                  LambdaArgType>::value;
 
     // Not using `std::make_unique` to avoid unnecessary instantiations of
     // `std::unique_ptr<HostKernel<...>>`. Only
     // `std::unique_ptr<HostKernelBase>` is necessary.
-    MHostKernel.reset(
-        new detail::HostKernel<KernelType, LambdaArgType, Dims>(KernelFunc));
+
+    MHostKernel.reset(new detail::HostKernel<KernelType, LambdaArgType, Dims>(
+        std::forward<KernelTypeUniversalRef>(KernelFunc)));
 
     constexpr bool KernelHasName =
         detail::getKernelName<KernelName>() != nullptr &&
@@ -739,7 +740,7 @@ class __SYCL_EXPORT handler {
 #ifdef __INTEL_SYCL_USE_INTEGRATION_HEADERS
     static_assert(
         !KernelHasName ||
-            sizeof(KernelFunc) == detail::getKernelSize<KernelName>(),
+            sizeof(KernelType) == detail::getKernelSize<KernelName>(),
         "Unexpected kernel lambda size. This can be caused by an "
         "external host compiler producing a lambda with an "
         "unexpected layout. This is a limitation of the compiler."
@@ -1133,7 +1134,7 @@ class __SYCL_EXPORT handler {
       typename KernelName, typename KernelType, int Dims,
       typename PropertiesT = ext::oneapi::experimental::empty_properties_t>
   void parallel_for_lambda_impl(range<Dims> UserRange, PropertiesT Props,
-                                KernelType KernelFunc) {
+                                const KernelType &KernelFunc) {
 #ifndef __SYCL_DEVICE_ONLY__
     throwIfActionIsCreated();
     throwOnKernelParameterMisuse<KernelName, KernelType>();
@@ -1545,19 +1546,21 @@ class __SYCL_EXPORT handler {
     // methods side.
 
     template <typename... TypesToForward, typename... ArgsTy>
-    static void kernel_single_task_unpack(handler *h, ArgsTy... Args) {
-      h->kernel_single_task<TypesToForward..., Props...>(Args...);
+    static void kernel_single_task_unpack(handler *h, ArgsTy&&... Args) {
+      h->kernel_single_task<TypesToForward..., Props...>(std::forward<ArgsTy>(Args)...);
     }
 
     template <typename... TypesToForward, typename... ArgsTy>
-    static void kernel_parallel_for_unpack(handler *h, ArgsTy... Args) {
-      h->kernel_parallel_for<TypesToForward..., Props...>(Args...);
+    static void kernel_parallel_for_unpack(handler *h, ArgsTy &&...Args) {
+      h->kernel_parallel_for<TypesToForward..., Props...>(
+          std::forward<ArgsTy>(Args)...);
     }
 
     template <typename... TypesToForward, typename... ArgsTy>
     static void kernel_parallel_for_work_group_unpack(handler *h,
-                                                      ArgsTy... Args) {
-      h->kernel_parallel_for_work_group<TypesToForward..., Props...>(Args...);
+                                                      ArgsTy &&...Args) {
+      h->kernel_parallel_for_work_group<TypesToForward..., Props...>(
+          std::forward<ArgsTy>(Args)...);
     }
   };
 
@@ -1622,9 +1625,9 @@ class __SYCL_EXPORT handler {
   void kernel_single_task_wrapper(const KernelType &KernelFunc) {
     unpack<KernelName, KernelType, PropertiesT,
            detail::KernelLambdaHasKernelHandlerArgT<KernelType>::value>(
-        KernelFunc, [&](auto Unpacker, auto... args) {
+        KernelFunc, [&](auto Unpacker, auto &&...args) {
           Unpacker.template kernel_single_task_unpack<KernelName, KernelType>(
-              args...);
+              std::forward<decltype(args)>(args)...);
         });
   }
 
@@ -1635,9 +1638,10 @@ class __SYCL_EXPORT handler {
     unpack<KernelName, KernelType, PropertiesT,
            detail::KernelLambdaHasKernelHandlerArgT<KernelType,
                                                     ElementType>::value>(
-        KernelFunc, [&](auto Unpacker, auto... args) {
+        KernelFunc, [&](auto Unpacker, auto &&...args) {
           Unpacker.template kernel_parallel_for_unpack<KernelName, ElementType,
-                                                       KernelType>(args...);
+                                                       KernelType>(
+              std::forward<decltype(args)>(args)...);
         });
   }
 
@@ -1648,9 +1652,10 @@ class __SYCL_EXPORT handler {
     unpack<KernelName, KernelType, PropertiesT,
            detail::KernelLambdaHasKernelHandlerArgT<KernelType,
                                                     ElementType>::value>(
-        KernelFunc, [&](auto Unpacker, auto... args) {
+        KernelFunc, [&](auto Unpacker, auto &&...args) {
           Unpacker.template kernel_parallel_for_work_group_unpack<
-              KernelName, ElementType, KernelType>(args...);
+              KernelName, ElementType, KernelType>(
+              std::forward<decltype(args)>(args)...);
         });
   }
 
@@ -1900,21 +1905,21 @@ class __SYCL_EXPORT handler {
   void parallel_for(range<1> NumWorkItems, const KernelType &KernelFunc) {
     parallel_for_lambda_impl<KernelName>(
         NumWorkItems, ext::oneapi::experimental::empty_properties_t{},
-        std::move(KernelFunc));
+        KernelFunc);
   }
 
   template <typename KernelName = detail::auto_name, typename KernelType>
   void parallel_for(range<2> NumWorkItems, const KernelType &KernelFunc) {
     parallel_for_lambda_impl<KernelName>(
         NumWorkItems, ext::oneapi::experimental::empty_properties_t{},
-        std::move(KernelFunc));
+        KernelFunc);
   }
 
   template <typename KernelName = detail::auto_name, typename KernelType>
   void parallel_for(range<3> NumWorkItems, const KernelType &KernelFunc) {
     parallel_for_lambda_impl<KernelName>(
         NumWorkItems, ext::oneapi::experimental::empty_properties_t{},
-        std::move(KernelFunc));
+        KernelFunc);
   }
 
   /// Enqueues a command to the SYCL runtime to invoke \p Func once.

sycl/test-e2e/Basic/test_num_kernel_copies.cpp

@@ -0,0 +1,43 @@
+// RUN: %{build} -o %t.out
+// RUN: %{run} %t.out
+
+#include <sycl/detail/core.hpp>
+
+size_t copy_count = 0;
+size_t move_count = 0;
+
+template <int N> class kernel {
+public:
+  kernel() {};
+  kernel(const kernel &other) { copy_count++; };
+  kernel(kernel &&other) { ++move_count; }
+
+  void operator()(sycl::id<1> id) const {}
+  void operator()(sycl::nd_item<1> id) const {}
+  void operator()() const {}
+};
+template <int N> struct sycl::is_device_copyable<kernel<N>> : std::true_type {};
+
+int main(int argc, char **argv) {
+  sycl::queue q;
+
+  kernel<0> krn0;
+  q.parallel_for(sycl::range<1>{1}, krn0);
+  assert(copy_count == 1);
+  assert(move_count == 0);
+  copy_count = 0;
+
+  kernel<1> krn1;
+  q.parallel_for(sycl::nd_range<1>{1, 1}, krn1);
+  assert(copy_count == 1);
+  assert(move_count == 0);
+  copy_count = 0;
+
+  kernel<2> krn2;
+  q.single_task(krn2);
+  assert(copy_count == 1);
+  assert(move_count == 0);
+  copy_count = 0;
+
+  return 0;
+}