native.arm.jscvt.ccm

// SPDX-License-Identifier: BSD-2-Clause OR Apache-2.0
module;
#include "native/isa_import.h"
#include "native/config.h"
#include "native/attributes.h"
#include "native/targets.h"
#include <bit>
#include <cstdint>
 
export module native.arm.jscvt;
export import native.arm.features;
 
namespace native::detail {
  constexpr std::int32_t jcvt_constant(double value) noexcept {
    auto bits = std::bit_cast<std::uint64_t>(value);
    auto exponent = unsigned((bits >> 52) & 0x7ff);
    // NaNs, infinities, zeros and magnitudes below one all convert to zero.
    if (exponent == 0x7ff || exponent < 1023) return 0;
    int shift = int(exponent) - 1023 - 52;
    if (shift >= 32) return 0;
    auto significand = (bits & 0x000fffffffffffffULL) | 0x0010000000000000ULL;
    auto result = shift >= 0 ? std::uint32_t(significand) << shift
                            : std::uint32_t(significand >> -shift);
    if (bits >> 63) result = std::uint32_t(0) - result;
    return std::bit_cast<std::int32_t>(result);
  }
}
 
#if NATIVE_HOST_NEON || defined(NATIVE_DOXYGEN)
export namespace native {

  template<isa<arm> Arch = NATIVE_BASELINE> requires(Arch.has(arm_feature::jsconv))
  native_nodiscard native_inline native_target("jsconv") constexpr std::int32_t
  jcvt(double value) noexcept {
    if consteval {
      return detail::jcvt_constant(value);
    } else {
      return __builtin_arm_jcvt(value);
    }
  }

  template<isa<arm> Arch = NATIVE_BASELINE> requires(!Arch.has(arm_feature::jsconv))
  native_nodiscard consteval std::int32_t jcvt(double value) noexcept {
    return detail::jcvt_constant(value);
  }

}
#endif