[libc-commits] [libc] [libc][math][c23] implement C23 math function asinpif16 (PR #146226)

[via libc-commits]

================
@@ -0,0 +1,151 @@
+//===-- Half-precision asinpif16(x) 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/asinpif16.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/PolyEval.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/macros/optimization.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+static constexpr size_t N_ASINPIF16_EXCEPTS = 3;
+
+static constexpr fputil::ExceptValues<float16, N_ASINPIF16_EXCEPTS>
+    ASINPIF16_EXCEPTS{{
+        // (input_hex, RZ_output_hex, RU_offset, RD_offset, RN_offset)
+        // x = 0.0, asinfpi(0.0) = 0.0
+        {0x0000, 0x0000, 0, 0, 0},
+
+        // x = 0x1.004p-3, asinpif16(x) = 0x1.47p-5 (RZ)
+        {0x3001U, 0x291cU, 1U, 0U, 1U},
+        // x = 0x1.0bp-1, asinpif16(x) = 0x1.658p-3 (RZ)
+        {0x382cU, 0x3196U, 1U, 0U, 0U},
+    }};
+
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+LLVM_LIBC_FUNCTION(float16, asinpif16, (float16 x)) {
+  using FPBits = fputil::FPBits<float16>;
+
+  FPBits xbits(x);
+  uint16_t x_uint = xbits.uintval();
+  bool is_neg = static_cast<bool>(x_uint >> 15);
----------------
lntue wrote:

`FPBits` has `is_neg()` and `abs()` methods.  You can have `x_abs() = xbits.abs().get_val()`.

https://github.com/llvm/llvm-project/pull/146226