[libc-commits] [libc] [llvm] [libc][math] Move hypot to shared/math and make it constexpr (PR #177588)

[Nico Weber via libc-commits]

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@@ -0,0 +1,219 @@
+//===-- Implementation header for hypot -------------------------*- 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_MATH_HYPOT_H
+#define LLVM_LIBC_SRC_SUPPORT_MATH_HYPOT_H
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/CPP/type_traits.h"
+#include "src/__support/FPUtil/BasicOperations.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/uint128.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace math {
+
+namespace internal {
+// Helper to find the leading one in a mantissa.
+template <typename T>
+LIBC_INLINE constexpr T find_leading_one(T mant, int &shift_length) {
+  shift_length = 0;
+  if (mant > 0) {
+    shift_length = (sizeof(mant) * 8) - 1 - cpp::countl_zero(mant);
+  }
+  return static_cast<T>((T(1) << shift_length));
+}
+
+// DoubleLength structure mapping
+template <typename T> struct DoubleLength;
+template <> struct DoubleLength<uint16_t> { using Type = uint32_t; };
+template <> struct DoubleLength<uint32_t> { using Type = uint64_t; };
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nico wrote:

Where did all this code come from? Why isn't this `return LIBC_NAMESPACE::fputil::hypot(x, y)` like in hypot.cpp?

https://github.com/llvm/llvm-project/pull/177588