[llvm] [libsycl] add USM alloc/free functions (PR #184111)

[Sergey Semenov via llvm-commits]

================
@@ -0,0 +1,130 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <sycl/__impl/usm_functions.hpp>
+
+#include <detail/device_impl.hpp>
+#include <detail/offload/offload_utils.hpp>
+
+#include <OffloadAPI.h>
+
+#include <algorithm>
+
+_LIBSYCL_BEGIN_NAMESPACE_SYCL
+
+// SYCL 2020 4.8.3.2. Device allocation functions.
+
+void *malloc_device(std::size_t numBytes, const device &syclDevice,
+                    const context &syclContext, const property_list &propList) {
+  return malloc(numBytes, syclDevice, syclContext, usm::alloc::device,
+                propList);
+}
+
+void *malloc_device(std::size_t numBytes, const queue &syclQueue,
+                    const property_list &propList) {
+  return malloc_device(numBytes, syclQueue.get_device(),
+                       syclQueue.get_context(), propList);
+}
+
+// SYCL 2020 4.8.3.3. Host allocation functions.
+
+void *malloc_host(std::size_t numBytes, const context &syclContext,
+                  const property_list &propList) {
+  auto ContextDevices = syclContext.get_devices();
+  assert(!ContextDevices.empty() && "Context can't be created without device");
+  if (std::none_of(
+          ContextDevices.begin(), ContextDevices.end(),
+          [](device Dev) { return Dev.has(aspect::usm_host_allocations); }))
+    throw sycl::exception(
+        sycl::errc::feature_not_supported,
+        "All devices of context do not support host USM allocations.");
+  return malloc(numBytes, ContextDevices[0], syclContext, usm::alloc::host,
+                propList);
+}
+
+void *malloc_host(std::size_t numBytes, const queue &syclQueue,
+                  const property_list &propList) {
+  return malloc_host(numBytes, syclQueue.get_context(), propList);
+}
+
+// SYCL 2020 4.8.3.4. Shared allocation functions.
+
+void *malloc_shared(std::size_t numBytes, const device &syclDevice,
+                    const context &syclContext, const property_list &propList) {
+  return malloc(numBytes, syclDevice, syclContext, usm::alloc::shared,
+                propList);
+}
+
+void *malloc_shared(std::size_t numBytes, const queue &syclQueue,
+                    const property_list &propList) {
+  return malloc_shared(numBytes, syclQueue.get_device(),
+                       syclQueue.get_context(), propList);
+}
+
+// SYCL 2020 4.8.3.5. Parameterized allocation functions.
+
+static aspect getAspectByAllocationKind(usm::alloc kind) {
+  switch (kind) {
+  case usm::alloc::host:
+    return aspect::usm_host_allocations;
+  case usm::alloc::device:
+    return aspect::usm_device_allocations;
+  case usm::alloc::shared:
+    return aspect::usm_shared_allocations;
+  default:
+    assert(false &&
+           "Must be unreachable, usm::unknown allocation can't be requested");
+    // usm::alloc::unknown can be returned to user from get_pointer_type but
+    // it can't be converted to a valid backend type and there is no need to
+    // do that.
+    throw exception(sycl::make_error_code(sycl::errc::runtime),
+                    "USM type is not supported");
----------------
sergey-semenov wrote:

```suggestion
  case usm::alloc::unknown:
    // usm::alloc::unknown can be returned to user from get_pointer_type but
    // it can't be converted to a valid backend type.
    throw exception(sycl::make_error_code(sycl::errc::invalid),
                    "Invalid USM allocation kind requested");
```
The code doesn't look unreachable since there doesn't seem to be any checks for `usm::alloc::unknown` elsewhere if the user passes it to `malloc`. Also, I would reword the error message since requesting an `unknown` allocation is not just unsupported, it doesn't make any sense.

https://github.com/llvm/llvm-project/pull/184111