//===-- floattidf.c - Implement __floattidf -------------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file implements __floattidf for the compiler_rt library. // //===----------------------------------------------------------------------===// #include "int_lib.h" #ifdef CRT_HAS_128BIT // Returns: convert a to a double, rounding toward even. // Assumption: double is a IEEE 64 bit floating point type // ti_int is a 128 bit integral type // seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm // mmmm COMPILER_RT_ABI double __floattidf(ti_int a) { if (a == 0) return 0.0; const unsigned N = sizeof(ti_int) * CHAR_BIT; const ti_int s = a >> (N - 1); a = (a ^ s) - s; int sd = N - __clzti2(a); // number of significant digits si_int e = sd - 1; // exponent if (sd > DBL_MANT_DIG) { // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR // 12345678901234567890123456 // 1 = msb 1 bit // P = bit DBL_MANT_DIG-1 bits to the right of 1 // Q = bit DBL_MANT_DIG bits to the right of 1 // R = "or" of all bits to the right of Q switch (sd) { case DBL_MANT_DIG + 1: a <<= 1; break; case DBL_MANT_DIG + 2: break; default: a = ((tu_int)a >> (sd - (DBL_MANT_DIG + 2))) | ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG + 2) - sd))) != 0); }; // finish: a |= (a & 4) != 0; // Or P into R ++a; // round - this step may add a significant bit a >>= 2; // dump Q and R // a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits if (a & ((tu_int)1 << DBL_MANT_DIG)) { a >>= 1; ++e; } // a is now rounded to DBL_MANT_DIG bits } else { a <<= (DBL_MANT_DIG - sd); // a is now rounded to DBL_MANT_DIG bits } double_bits fb; fb.u.s.high = ((su_int)s & 0x80000000) | // sign ((e + 1023) << 20) | // exponent ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high fb.u.s.low = (su_int)a; // mantissa-low return fb.f; } #endif // CRT_HAS_128BIT