1*0b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 2*0b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 3*0b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 4*0b57cec5SDimitry Andric 5*0b57cec5SDimitry Andric // long double __floatunditf(unsigned long long x); 6*0b57cec5SDimitry Andric // This file implements the PowerPC unsigned long long -> long double conversion 7*0b57cec5SDimitry Andric 8*0b57cec5SDimitry Andric #include "DD.h" 9*0b57cec5SDimitry Andric __floatunditf(uint64_t a)10*0b57cec5SDimitry Andriclong double __floatunditf(uint64_t a) { 11*0b57cec5SDimitry Andric 12*0b57cec5SDimitry Andric // Begins with an exact copy of the code from __floatundidf 13*0b57cec5SDimitry Andric 14*0b57cec5SDimitry Andric static const double twop52 = 0x1.0p52; 15*0b57cec5SDimitry Andric static const double twop84 = 0x1.0p84; 16*0b57cec5SDimitry Andric static const double twop84_plus_twop52 = 0x1.00000001p84; 17*0b57cec5SDimitry Andric 18*0b57cec5SDimitry Andric doublebits high = {.d = twop84}; 19*0b57cec5SDimitry Andric doublebits low = {.d = twop52}; 20*0b57cec5SDimitry Andric 21*0b57cec5SDimitry Andric high.x |= a >> 32; // 0x1.0p84 + high 32 bits of a 22*0b57cec5SDimitry Andric low.x |= a & UINT64_C(0x00000000ffffffff); // 0x1.0p52 + low 32 bits of a 23*0b57cec5SDimitry Andric 24*0b57cec5SDimitry Andric const double high_addend = high.d - twop84_plus_twop52; 25*0b57cec5SDimitry Andric 26*0b57cec5SDimitry Andric // At this point, we have two double precision numbers 27*0b57cec5SDimitry Andric // high_addend and low.d, and we wish to return their sum 28*0b57cec5SDimitry Andric // as a canonicalized long double: 29*0b57cec5SDimitry Andric 30*0b57cec5SDimitry Andric // This implementation sets the inexact flag spuriously. 31*0b57cec5SDimitry Andric // This could be avoided, but at some substantial cost. 32*0b57cec5SDimitry Andric 33*0b57cec5SDimitry Andric DD result; 34*0b57cec5SDimitry Andric 35*0b57cec5SDimitry Andric result.s.hi = high_addend + low.d; 36*0b57cec5SDimitry Andric result.s.lo = (high_addend - result.s.hi) + low.d; 37*0b57cec5SDimitry Andric 38*0b57cec5SDimitry Andric return result.ld; 39*0b57cec5SDimitry Andric } 40