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

[Sergey Semenov via llvm-commits]

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@@ -0,0 +1,124 @@
+// REQUIRES: any-device
+// RUN: %clangxx %sycl_options %s -o %t.out
+// RUN: %t.out
+
+#include <sycl/sycl.hpp>
+
+#include <cstddef>
+#include <iostream>
+#include <tuple>
+
+using namespace sycl;
+
+constexpr size_t Align = 256;
+
+struct alignas(Align) Aligned {
+  int x;
+};
+
+int main() {
+  queue q;
+  context ctx = q.get_context();
+  device d = q.get_device();
+
+  auto check = [&q](size_t Alignment, auto AllocFn, int Line = __builtin_LINE(),
+                    int Case = 0) {
+    // First allocation might naturally be over-aligned. Do several of them to
+    // do the verification;
+    decltype(AllocFn()) Arr[10];
+    for (auto *&Elem : Arr)
+      Elem = AllocFn();
+    for (auto *Ptr : Arr) {
+      auto v = reinterpret_cast<uintptr_t>(Ptr);
+      if ((v & (Alignment - 1)) != 0) {
+        std::cout << "Failed at line " << Line << ", case " << Case
+                  << std::endl;
+        assert(false && "Not properly aligned!");
+        break; // To be used with commented out assert above.
+      }
+    }
+    for (auto *Ptr : Arr)
+      free(Ptr, q);
+  };
+
+  // The strictest (largest) fundamental alignment of any type is the alignment
+  // of max_align_t. This is, however, smaller than the minimal alignment
+  // returned by the underlyging runtime as of now.
----------------
sergey-semenov wrote:

```suggestion
  // returned by the underlying runtime as of now.
```

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