[libc-commits] [libc] [libc][math][c++23] Add bfloat16 support in LLVM libc (PR #144463)

[via libc-commits]

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@@ -0,0 +1,63 @@
+//===-- Definition of bfloat16 data type. -----------------------*- C++ -*-===//
+//
+// 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 LLVM_LIBC_SRC___SUPPORT_FPUTIL_BFLOAT16_H
+#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_BFLOAT16_H
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/CPP/type_traits.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/__support/FPUtil/dyadic_float.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+#include <stdint.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+struct BFloat16 {
+  uint16_t bits;
+
+  LIBC_INLINE BFloat16() = default;
+
+  LIBC_INLINE constexpr explicit BFloat16(uint16_t bits) : bits(bits) {}
+
+  template <typename T> LIBC_INLINE constexpr explicit BFloat16(T value) {
+    if constexpr (cpp::is_floating_point_v<T>) {
+      bits = fputil::cast<bfloat16>(value).bits;
+    } else if constexpr (cpp::is_integral_v<T>) {
+      Sign sign = Sign::POS;
+
+      if constexpr (cpp::is_signed_v<T>) {
+        if (value < 0) {
+          sign = Sign::NEG;
+          value = -value;
+        }
+      }
+
+      fputil::DyadicFloat<cpp::numeric_limits<cpp::make_unsigned_t<T>>::digits>
+          xd(sign, 0, value);
+      bits = xd.template as<bfloat16, /*ShouldSignalExceptions=*/true>().bits;
+
+    } else {
+      bits = fputil::cast<bfloat16>(static_cast<float>(value)).bits;
+    }
+  }
+
+  template <cpp::enable_if_t<fputil::get_fp_type<float>() ==
+                                 fputil::FPType::IEEE754_Binary32,
+                             int> = 0>
+  operator float() const {
----------------
overmighty wrote:

```suggestion
  LIBC_INLINE constexpr operator float() const {
```

https://github.com/llvm/llvm-project/pull/144463