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

[via libc-commits]

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+//===-- 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 = xbits.is_neg();
+  float16 x_abs = xbits.abs().get_val();
+
+  auto signed_result = [is_neg](auto r) -> auto { return is_neg ? -r : r; };
+
+  if (LIBC_UNLIKELY(x_abs > 1.0f16)) {
+    // aspinf16(NaN) = NaN
+    if (xbits.is_nan()) {
+      if (xbits.is_signaling_nan()) {
+        fputil::raise_except_if_required(FE_INVALID);
+        return FPBits::quiet_nan().get_val();
+      }
+      return x;
+    }
+
+    // 1 < |x| <= +/-inf
+    fputil::raise_except_if_required(FE_INVALID);
+    fputil::set_errno_if_required(EDOM);
+
+    return FPBits::quiet_nan().get_val();
+  }
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+  // exceptional values
+  if (auto r = ASINPIF16_EXCEPTS.lookup(x_uint); LIBC_UNLIKELY(r.has_value()))
+    return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
----------------
overmighty wrote:

```suggestion
```

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