[libc-commits] [libc] [libc][math][c23] Add acoshf16 C23 math function. (PR #130588)

[Harrison Hao via libc-commits]

================
@@ -0,0 +1,98 @@
+//===-- Half-precision acoshf16 function -----------------------------------===//
+//
+// 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 "src/math/acoshf16.h"
+#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/macros/optimization.h"
+#include "src/math/generic/common_constants.h"
+#include "src/math/generic/explogxf.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(float16, acoshf16, (float16 x)) {
+  using FPBits = fputil::FPBits<float16>;
+  FPBits xbits(x);
+  uint16_t x_u = xbits.uintval();
+  uint16_t x_abs = x_u & 0x7fff;
+
+//   if (LIBC_UNLIKELY(x <= 1.0f)) {
+//     if (x == 1.0f)
+//       return 0.0f;
+//     // x < 1.
+//     fputil::set_errno_if_required(EDOM);
+//     fputil::raise_except_if_required(FE_INVALID);
+//     return FPBits::quiet_nan().get_val();
+//   }
+  
+  // Check for NaN input first.
+  if (LIBC_UNLIKELY(xbits.is_nan())) {
+    if (xbits.is_signaling_nan()) {
+      fputil::raise_except(FE_INVALID);
+      return FPBits::quiet_nan().get_val();
+    }
+    return x;
+  }
+
+  // Check for infinite inputs.
+  if (LIBC_UNLIKELY(xbits.is_inf())) {
+    if (xbits.is_neg()) {
+      fputil::set_errno_if_required(EDOM);
+      fputil::raise_except(FE_INVALID);
+      return FPBits::quiet_nan().get_val();
+    }
+    return x;
+  }
+
+  // Domain error for inputs less than 1.0.
+  if (LIBC_UNLIKELY(x_abs < 0x3c00)) {
+    fputil::set_errno_if_required(EDOM);
+    fputil::raise_except(FE_INVALID);
+    return FPBits::quiet_nan().get_val();
+  }
+
+  // acosh(1.0) exactly equals 0.0
+  if (LIBC_UNLIKELY(xbits.uintval() == 0x3c00U))
+    return float16(0.0f);
+
+  float xf32 = static_cast<float>(x);
+
+  // High precision for inputs very close to 1.0
+  if (LIBC_UNLIKELY(xf32 < 1.25f)) {
+    float delta = xf32 - 1.0f;
+    float sqrt_2 = fputil::sqrt<float>(2.0f * delta);
+    float sqrt_2d = fputil::sqrt<float>(2.0f * delta);
+    float d32 = delta * fputil::sqrt<float>(delta);
+    float term2 = d32 / (6.0f * fputil::sqrt<float>(2.0f));
+    float d52 = d32 * delta;
+    float term3 = 3.0f * d52 / (80.0f * sqrt_2);
+    float d72 = d52 * delta;
+    float term4 = 5.0f * d72 / (1792.0f * sqrt_2);
+    float result = sqrt_2d - term2 + term3 - term4;
+    return fputil::cast<float16>(result);
+  }
+
+  // Special optimization for large input values.
+  if (LIBC_UNLIKELY(xf32 >= 32.0f)) {
+    float result = static_cast<float>(log_eval(2.0f * xf32));
+    return fputil::cast<float16>(result);
+  }
+
+  // Standard computation for general case.
+  float sqrt_term = fputil::sqrt<float>(fputil::multiply_add(xf32, xf32, -1.0f));
+  float result = static_cast<float>(log_eval(xf32 + sqrt_term));
+
+  return fputil::cast<float16>(result);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
----------------
harrisonGPU wrote:

Done.

https://github.com/llvm/llvm-project/pull/130588