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-exception 4 5 // uint64_t __fixunstfdi(long double x); 6 // This file implements the PowerPC 128-bit double-double -> uint64_t conversion 7 8 #include "DD.h" 9 __fixunstfdi(long double input)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 bit 23 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 integer 37 38 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; 39 40 // Shift the tail mantissa into the right position, accounting for the 41 // 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 else 56 return UINT64_MAX; 57 } 58