1*0b57cec5SDimitry Andric //===-- floattidf.c - Implement __floattidf -------------------------------===// 2*0b57cec5SDimitry Andric // 3*0b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*0b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*0b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*0b57cec5SDimitry Andric // 7*0b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 8*0b57cec5SDimitry Andric // 9*0b57cec5SDimitry Andric // This file implements __floattidf for the compiler_rt library. 10*0b57cec5SDimitry Andric // 11*0b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 12*0b57cec5SDimitry Andric 13*0b57cec5SDimitry Andric #include "int_lib.h" 14*0b57cec5SDimitry Andric 15*0b57cec5SDimitry Andric #ifdef CRT_HAS_128BIT 16*0b57cec5SDimitry Andric 17*0b57cec5SDimitry Andric // Returns: convert a to a double, rounding toward even. 18*0b57cec5SDimitry Andric 19*0b57cec5SDimitry Andric // Assumption: double is a IEEE 64 bit floating point type 20*0b57cec5SDimitry Andric // ti_int is a 128 bit integral type 21*0b57cec5SDimitry Andric 22*0b57cec5SDimitry Andric // seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm 23*0b57cec5SDimitry Andric // mmmm 24*0b57cec5SDimitry Andric 25*0b57cec5SDimitry Andric COMPILER_RT_ABI double __floattidf(ti_int a) { 26*0b57cec5SDimitry Andric if (a == 0) 27*0b57cec5SDimitry Andric return 0.0; 28*0b57cec5SDimitry Andric const unsigned N = sizeof(ti_int) * CHAR_BIT; 29*0b57cec5SDimitry Andric const ti_int s = a >> (N - 1); 30*0b57cec5SDimitry Andric a = (a ^ s) - s; 31*0b57cec5SDimitry Andric int sd = N - __clzti2(a); // number of significant digits 32*0b57cec5SDimitry Andric int e = sd - 1; // exponent 33*0b57cec5SDimitry Andric if (sd > DBL_MANT_DIG) { 34*0b57cec5SDimitry Andric // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 35*0b57cec5SDimitry Andric // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 36*0b57cec5SDimitry Andric // 12345678901234567890123456 37*0b57cec5SDimitry Andric // 1 = msb 1 bit 38*0b57cec5SDimitry Andric // P = bit DBL_MANT_DIG-1 bits to the right of 1 39*0b57cec5SDimitry Andric // Q = bit DBL_MANT_DIG bits to the right of 1 40*0b57cec5SDimitry Andric // R = "or" of all bits to the right of Q 41*0b57cec5SDimitry Andric switch (sd) { 42*0b57cec5SDimitry Andric case DBL_MANT_DIG + 1: 43*0b57cec5SDimitry Andric a <<= 1; 44*0b57cec5SDimitry Andric break; 45*0b57cec5SDimitry Andric case DBL_MANT_DIG + 2: 46*0b57cec5SDimitry Andric break; 47*0b57cec5SDimitry Andric default: 48*0b57cec5SDimitry Andric a = ((tu_int)a >> (sd - (DBL_MANT_DIG + 2))) | 49*0b57cec5SDimitry Andric ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG + 2) - sd))) != 0); 50*0b57cec5SDimitry Andric }; 51*0b57cec5SDimitry Andric // finish: 52*0b57cec5SDimitry Andric a |= (a & 4) != 0; // Or P into R 53*0b57cec5SDimitry Andric ++a; // round - this step may add a significant bit 54*0b57cec5SDimitry Andric a >>= 2; // dump Q and R 55*0b57cec5SDimitry Andric // a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits 56*0b57cec5SDimitry Andric if (a & ((tu_int)1 << DBL_MANT_DIG)) { 57*0b57cec5SDimitry Andric a >>= 1; 58*0b57cec5SDimitry Andric ++e; 59*0b57cec5SDimitry Andric } 60*0b57cec5SDimitry Andric // a is now rounded to DBL_MANT_DIG bits 61*0b57cec5SDimitry Andric } else { 62*0b57cec5SDimitry Andric a <<= (DBL_MANT_DIG - sd); 63*0b57cec5SDimitry Andric // a is now rounded to DBL_MANT_DIG bits 64*0b57cec5SDimitry Andric } 65*0b57cec5SDimitry Andric double_bits fb; 66*0b57cec5SDimitry Andric fb.u.s.high = ((su_int)s & 0x80000000) | // sign 67*0b57cec5SDimitry Andric ((e + 1023) << 20) | // exponent 68*0b57cec5SDimitry Andric ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high 69*0b57cec5SDimitry Andric fb.u.s.low = (su_int)a; // mantissa-low 70*0b57cec5SDimitry Andric return fb.f; 71*0b57cec5SDimitry Andric } 72*0b57cec5SDimitry Andric 73*0b57cec5SDimitry Andric #endif // CRT_HAS_128BIT 74