Add OpenMP support

third_party/openmp/kmp_utils.h

@@ -0,0 +1,55 @@
+/*
+ * kmp_utils.h -- Utilities that used internally
+ */
+
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+#ifndef __KMP_UTILS_H__
+#define __KMP_UTILS_H__
+
+#include <cstddef>
+
+#include "kmp.h"
+
+/// A simple pure header implementation of VLA that aims to replace uses of
+/// actual VLA, which can cause compile warning. This class by default creates a
+/// stack buffer that can accomodate \p N elements. If the number of elements is
+/// greater than \p N, then a heap buffer will be allocated and used to
+/// accomodate the elements. Similar to the actual VLA, we don't check boundary
+/// (for now), so we will not store the number of elements. We can always revise
+/// it later.
+template <typename T, unsigned N = 8> class SimpleVLA final {
+  T StackBuffer[N];
+  T *HeapBuffer = nullptr;
+  T *Ptr = StackBuffer;
+
+public:
+  SimpleVLA() = delete;
+  SimpleVLA(const SimpleVLA &) = delete;
+  SimpleVLA(SimpleVLA &&) = delete;
+  SimpleVLA &operator=(const SimpleVLA &) = delete;
+  SimpleVLA &operator=(SimpleVLA &&) = delete;
+
+  explicit SimpleVLA(unsigned NumOfElements) noexcept {
+    if (NumOfElements > N) {
+      HeapBuffer =
+          reinterpret_cast<T *>(__kmp_allocate(NumOfElements * sizeof(T)));
+      Ptr = HeapBuffer;
+    }
+  }
+
+  ~SimpleVLA() {
+    if (HeapBuffer)
+      __kmp_free(HeapBuffer);
+  }
+
+  operator T *() noexcept { return Ptr; }
+  operator const T *() const noexcept { return Ptr; }
+};
+
+#endif