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1// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.2// See https://llvm.org/LICENSE.txt for license information.3// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception4 5// uint64_t __fixunstfdi(long double x);6// This file implements the PowerPC 128-bit double-double -> uint64_t conversion7 8#include "DD.h"9 10uint64_t __fixunstfdi(long double input) {11 const DD x = {.ld = input};12 const doublebits hibits = {.d = x.s.hi};13 14 const uint32_t highWordMinusOne =15 (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000);16 17 // If (1.0 - tiny) <= input < 0x1.0p64:18 if (UINT32_C(0x04000000) > highWordMinusOne) {19 const int unbiasedHeadExponent = highWordMinusOne >> 20;20 21 uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); // mantissa(hi)22 result |= UINT64_C(0x0010000000000000); // matissa(hi) with implicit bit23 result <<= 11; // mantissa(hi) left aligned in the int64 field.24 25 // If the tail is non-zero, we need to patch in the tail bits.26 if (0.0 != x.s.lo) {27 const doublebits lobits = {.d = x.s.lo};28 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);29 tailMantissa |= INT64_C(0x0010000000000000);30 31 // At this point we have the mantissa of |tail|32 33 const int64_t negationMask = ((int64_t)(lobits.x)) >> 63;34 tailMantissa = (tailMantissa ^ negationMask) - negationMask;35 36 // Now we have the mantissa of tail as a signed 2s-complement integer37 38 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;39 40 // Shift the tail mantissa into the right position, accounting for the41 // bias of 11 that we shifted the head mantissa by.42 tailMantissa >>=43 (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11)));44 45 result += tailMantissa;46 }47 48 result >>= (63 - unbiasedHeadExponent);49 return result;50 }51 52 // Edge cases are handled here, with saturation.53 if (1.0 > x.s.hi)54 return UINT64_C(0);55 else56 return UINT64_MAX;57}58