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1//===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-C -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements converting a signed 128 bit integer to a 128bit IBM /10// PowerPC long double (double-double) value.11//12//===----------------------------------------------------------------------===//13 14#include <stdint.h>15 16// Conversions from signed and unsigned 64-bit int to long double.17long double __floatditf(int64_t);18long double __floatunditf(uint64_t);19 20// Convert a signed 128-bit integer to long double.21// This uses the following property: Let hi and lo be 64-bits each,22// and let signed_val_k() and unsigned_val_k() be the value of the23// argument interpreted as a signed or unsigned k-bit integer. Then,24//25// signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo)26// = (long double)hi * 2^64 + (long double)lo,27//28// where (long double)hi and (long double)lo are signed and29// unsigned 64-bit integer to long double conversions, respectively.30long double __floattitf(__int128_t arg) {31 // Split the int128 argument into 64-bit high and low int64 parts.32 int64_t ArgHiPart = (int64_t)(arg >> 64);33 uint64_t ArgLoPart = (uint64_t)arg;34 35 // Convert each 64-bit part into long double. The high part36 // must be a signed conversion and the low part an unsigned conversion37 // to ensure the correct result.38 long double ConvertedHiPart = __floatditf(ArgHiPart);39 long double ConvertedLoPart = __floatunditf(ArgLoPart);40 41 // The low bit of ArgHiPart corresponds to the 2^64 bit in arg.42 // Multiply the high part by 2^64 to undo the right shift by 64-bits43 // done in the splitting. Then, add to the low part to obtain the44 // final result.45 return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart);46}47