1*3cab2bb3Spatrick //===-- lib/floattitf.c - int128 -> quad-precision conversion -----*- C -*-===// 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 ti_int to quad-precision conversion for the 10*3cab2bb3Spatrick // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even 11*3cab2bb3Spatrick // mode. 12*3cab2bb3Spatrick // 13*3cab2bb3Spatrick //===----------------------------------------------------------------------===// 14*3cab2bb3Spatrick 15*3cab2bb3Spatrick #define QUAD_PRECISION 16*3cab2bb3Spatrick #include "fp_lib.h" 17*3cab2bb3Spatrick #include "int_lib.h" 18*3cab2bb3Spatrick 19*3cab2bb3Spatrick // Returns: convert a ti_int to a fp_t, rounding toward even. 20*3cab2bb3Spatrick 21*3cab2bb3Spatrick // Assumption: fp_t is a IEEE 128 bit floating point type 22*3cab2bb3Spatrick // ti_int is a 128 bit integral type 23*3cab2bb3Spatrick 24*3cab2bb3Spatrick // seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm 25*3cab2bb3Spatrick // mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm 26*3cab2bb3Spatrick // mmmm mmmm mmmm 27*3cab2bb3Spatrick 28*3cab2bb3Spatrick #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT) __floattitf(ti_int a)29*3cab2bb3SpatrickCOMPILER_RT_ABI fp_t __floattitf(ti_int a) { 30*3cab2bb3Spatrick if (a == 0) 31*3cab2bb3Spatrick return 0.0; 32*3cab2bb3Spatrick const unsigned N = sizeof(ti_int) * CHAR_BIT; 33*3cab2bb3Spatrick const ti_int s = a >> (N - 1); 34*3cab2bb3Spatrick a = (a ^ s) - s; 35*3cab2bb3Spatrick int sd = N - __clzti2(a); // number of significant digits 36*3cab2bb3Spatrick int e = sd - 1; // exponent 37*3cab2bb3Spatrick if (sd > LDBL_MANT_DIG) { 38*3cab2bb3Spatrick // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 39*3cab2bb3Spatrick // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 40*3cab2bb3Spatrick // 12345678901234567890123456 41*3cab2bb3Spatrick // 1 = msb 1 bit 42*3cab2bb3Spatrick // P = bit LDBL_MANT_DIG-1 bits to the right of 1 43*3cab2bb3Spatrick // Q = bit LDBL_MANT_DIG bits to the right of 1 44*3cab2bb3Spatrick // R = "or" of all bits to the right of Q 45*3cab2bb3Spatrick switch (sd) { 46*3cab2bb3Spatrick case LDBL_MANT_DIG + 1: 47*3cab2bb3Spatrick a <<= 1; 48*3cab2bb3Spatrick break; 49*3cab2bb3Spatrick case LDBL_MANT_DIG + 2: 50*3cab2bb3Spatrick break; 51*3cab2bb3Spatrick default: 52*3cab2bb3Spatrick a = ((tu_int)a >> (sd - (LDBL_MANT_DIG + 2))) | 53*3cab2bb3Spatrick ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG + 2) - sd))) != 0); 54*3cab2bb3Spatrick }; 55*3cab2bb3Spatrick // finish: 56*3cab2bb3Spatrick a |= (a & 4) != 0; // Or P into R 57*3cab2bb3Spatrick ++a; // round - this step may add a significant bit 58*3cab2bb3Spatrick a >>= 2; // dump Q and R 59*3cab2bb3Spatrick // a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits 60*3cab2bb3Spatrick if (a & ((tu_int)1 << LDBL_MANT_DIG)) { 61*3cab2bb3Spatrick a >>= 1; 62*3cab2bb3Spatrick ++e; 63*3cab2bb3Spatrick } 64*3cab2bb3Spatrick // a is now rounded to LDBL_MANT_DIG bits 65*3cab2bb3Spatrick } else { 66*3cab2bb3Spatrick a <<= (LDBL_MANT_DIG - sd); 67*3cab2bb3Spatrick // a is now rounded to LDBL_MANT_DIG bits 68*3cab2bb3Spatrick } 69*3cab2bb3Spatrick 70*3cab2bb3Spatrick long_double_bits fb; 71*3cab2bb3Spatrick fb.u.high.all = (s & 0x8000000000000000LL) // sign 72*3cab2bb3Spatrick | (du_int)(e + 16383) << 48 // exponent 73*3cab2bb3Spatrick | ((a >> 64) & 0x0000ffffffffffffLL); // significand 74*3cab2bb3Spatrick fb.u.low.all = (du_int)(a); 75*3cab2bb3Spatrick return fb.f; 76*3cab2bb3Spatrick } 77*3cab2bb3Spatrick 78*3cab2bb3Spatrick #endif 79