1*3cab2bb3Spatrick //===-- floattidf.c - Implement __floattidf -------------------------------===// 2*3cab2bb3Spatrick // 3*3cab2bb3Spatrick // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*3cab2bb3Spatrick // See https://llvm.org/LICENSE.txt for license information. 5*3cab2bb3Spatrick // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*3cab2bb3Spatrick // 7*3cab2bb3Spatrick //===----------------------------------------------------------------------===// 8*3cab2bb3Spatrick // 9*3cab2bb3Spatrick // This file implements __floattidf for the compiler_rt library. 10*3cab2bb3Spatrick // 11*3cab2bb3Spatrick //===----------------------------------------------------------------------===// 12*3cab2bb3Spatrick 13*3cab2bb3Spatrick #include "int_lib.h" 14*3cab2bb3Spatrick 15*3cab2bb3Spatrick #ifdef CRT_HAS_128BIT 16*3cab2bb3Spatrick 17*3cab2bb3Spatrick // Returns: convert a to a double, rounding toward even. 18*3cab2bb3Spatrick 19*3cab2bb3Spatrick // Assumption: double is a IEEE 64 bit floating point type 20*3cab2bb3Spatrick // ti_int is a 128 bit integral type 21*3cab2bb3Spatrick 22*3cab2bb3Spatrick // seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm 23*3cab2bb3Spatrick // mmmm 24*3cab2bb3Spatrick __floattidf(ti_int a)25*3cab2bb3SpatrickCOMPILER_RT_ABI double __floattidf(ti_int a) { 26*3cab2bb3Spatrick if (a == 0) 27*3cab2bb3Spatrick return 0.0; 28*3cab2bb3Spatrick const unsigned N = sizeof(ti_int) * CHAR_BIT; 29*3cab2bb3Spatrick const ti_int s = a >> (N - 1); 30*3cab2bb3Spatrick a = (a ^ s) - s; 31*3cab2bb3Spatrick int sd = N - __clzti2(a); // number of significant digits 32*3cab2bb3Spatrick int e = sd - 1; // exponent 33*3cab2bb3Spatrick if (sd > DBL_MANT_DIG) { 34*3cab2bb3Spatrick // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 35*3cab2bb3Spatrick // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 36*3cab2bb3Spatrick // 12345678901234567890123456 37*3cab2bb3Spatrick // 1 = msb 1 bit 38*3cab2bb3Spatrick // P = bit DBL_MANT_DIG-1 bits to the right of 1 39*3cab2bb3Spatrick // Q = bit DBL_MANT_DIG bits to the right of 1 40*3cab2bb3Spatrick // R = "or" of all bits to the right of Q 41*3cab2bb3Spatrick switch (sd) { 42*3cab2bb3Spatrick case DBL_MANT_DIG + 1: 43*3cab2bb3Spatrick a <<= 1; 44*3cab2bb3Spatrick break; 45*3cab2bb3Spatrick case DBL_MANT_DIG + 2: 46*3cab2bb3Spatrick break; 47*3cab2bb3Spatrick default: 48*3cab2bb3Spatrick a = ((tu_int)a >> (sd - (DBL_MANT_DIG + 2))) | 49*3cab2bb3Spatrick ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG + 2) - sd))) != 0); 50*3cab2bb3Spatrick }; 51*3cab2bb3Spatrick // finish: 52*3cab2bb3Spatrick a |= (a & 4) != 0; // Or P into R 53*3cab2bb3Spatrick ++a; // round - this step may add a significant bit 54*3cab2bb3Spatrick a >>= 2; // dump Q and R 55*3cab2bb3Spatrick // a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits 56*3cab2bb3Spatrick if (a & ((tu_int)1 << DBL_MANT_DIG)) { 57*3cab2bb3Spatrick a >>= 1; 58*3cab2bb3Spatrick ++e; 59*3cab2bb3Spatrick } 60*3cab2bb3Spatrick // a is now rounded to DBL_MANT_DIG bits 61*3cab2bb3Spatrick } else { 62*3cab2bb3Spatrick a <<= (DBL_MANT_DIG - sd); 63*3cab2bb3Spatrick // a is now rounded to DBL_MANT_DIG bits 64*3cab2bb3Spatrick } 65*3cab2bb3Spatrick double_bits fb; 66*3cab2bb3Spatrick fb.u.s.high = ((su_int)s & 0x80000000) | // sign 67*3cab2bb3Spatrick ((e + 1023) << 20) | // exponent 68*3cab2bb3Spatrick ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high 69*3cab2bb3Spatrick fb.u.s.low = (su_int)a; // mantissa-low 70*3cab2bb3Spatrick return fb.f; 71*3cab2bb3Spatrick } 72*3cab2bb3Spatrick 73*3cab2bb3Spatrick #endif // CRT_HAS_128BIT 74