[SYCL] Add support for the SYCL_INTEL_local_memory extension to headers

sycl/include/CL/sycl.hpp

@@ -28,6 +28,7 @@
 #include <CL/sycl/exception.hpp>
 #include <CL/sycl/feature_test.hpp>
 #include <CL/sycl/group.hpp>
+#include <CL/sycl/group_local_memory.hpp>
 #include <CL/sycl/handler.hpp>
 #include <CL/sycl/id.hpp>
 #include <CL/sycl/image.hpp>

sycl/include/CL/sycl/detail/sycl_fe_intrins.hpp

@@ -10,6 +10,9 @@
 
 #pragma once
 
+#include <cstddef>
+#include <cstdint>
+
 #ifdef __SYCL_DEVICE_ONLY__
 
 // Get the value of the specialization constant with given name.
@@ -42,4 +45,8 @@ SYCL_EXTERNAL T __sycl_getComposite2020SpecConstantValue(const char *SymbolicID,
                                                          void *DefaultValue,
                                                          void *RTBuffer);
 
+// Request a fixed-size allocation in local address space at kernel scope.
+extern "C" SYCL_EXTERNAL __attribute__((opencl_local)) std::uint8_t *
+__sycl_allocateLocalMemory(std::size_t Size, std::size_t Alignment);
+
 #endif

sycl/include/CL/sycl/group_local_memory.hpp

@@ -0,0 +1,67 @@
+//==----- group_local_memory.hpp --- SYCL group local memory extension -----==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#pragma once
+
+#include <CL/__spirv/spirv_vars.hpp>
+#include <CL/sycl/detail/defines_elementary.hpp>
+#include <CL/sycl/detail/sycl_fe_intrins.hpp>
+#include <CL/sycl/detail/type_traits.hpp>
+#include <CL/sycl/exception.hpp>
+#include <CL/sycl/group.hpp>
+#include <CL/sycl/multi_ptr.hpp>
+
+#include <cstdint>
+#include <type_traits>
+#include <utility>
+
+__SYCL_INLINE_NAMESPACE(cl) {
+namespace sycl {
+
+template <typename T, typename Group>
+std::enable_if_t<std::is_trivially_destructible<T>::value &&
+                     detail::is_group<Group>::value,
+                 multi_ptr<T, access::address_space::local_space>>
+    __SYCL_ALWAYS_INLINE group_local_memory_for_overwrite(Group g) {
+  (void)g;
+#ifdef __SYCL_DEVICE_ONLY__
+  __attribute__((opencl_local)) std::uint8_t *AllocatedMem =
+      __sycl_allocateLocalMemory(sizeof(T), alignof(T));
+  return reinterpret_cast<__attribute__((opencl_local)) T *>(AllocatedMem);
+#else
+  throw feature_not_supported(
+      "SYCL_INTEL_local_memory extension is not supported on host device",
+      PI_INVALID_OPERATION);
+#endif
+}
+
+template <typename T, typename Group, typename... Args>
+std::enable_if_t<std::is_trivially_destructible<T>::value &&
+                     detail::is_group<Group>::value,
+                 multi_ptr<T, access::address_space::local_space>>
+    __SYCL_ALWAYS_INLINE group_local_memory(Group g, Args &&... args) {
+  (void)g;
+#ifdef __SYCL_DEVICE_ONLY__
+  __attribute__((opencl_local)) std::uint8_t *AllocatedMem =
+      __sycl_allocateLocalMemory(sizeof(T), alignof(T));
+
+  // TODO switch to using group::get_local_linear_id here once it's implemented
+  id<3> Id = __spirv::initLocalInvocationId<3, id<3>>();
+  if (Id == id<3>(0, 0, 0))
+    new (AllocatedMem) T(std::forward<Args>(args)...);
+  detail::workGroupBarrier();
+  return reinterpret_cast<__attribute__((opencl_local)) T *>(AllocatedMem);
+#else
+  // Silence unused variable warning
+  [&args...] {}();
+  throw feature_not_supported(
+      "SYCL_INTEL_local_memory extension is not supported on host device",
+      PI_INVALID_OPERATION);
+#endif
+}
+} // namespace sycl
+} // __SYCL_INLINE_NAMESPACE(cl)