1353358Sdim//===-- floatundisf.c - Implement __floatundisf ---------------------------===// 2353358Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6353358Sdim// 7353358Sdim//===----------------------------------------------------------------------===// 8353358Sdim// 9353358Sdim// This file implements __floatundisf for the compiler_rt library. 10353358Sdim// 11353358Sdim//===----------------------------------------------------------------------===// 12276789Sdim 13353358Sdim// Returns: convert a to a float, rounding toward even. 14276789Sdim 15353358Sdim// Assumption: float is a IEEE 32 bit floating point type 16353358Sdim// du_int is a 64 bit integral type 17276789Sdim 18353358Sdim// seee eeee emmm mmmm mmmm mmmm mmmm mmmm 19276789Sdim 20276789Sdim#include "int_lib.h" 21276789Sdim 22353358SdimCOMPILER_RT_ABI float __floatundisf(du_int a) { 23353358Sdim if (a == 0) 24353358Sdim return 0.0F; 25353358Sdim const unsigned N = sizeof(du_int) * CHAR_BIT; 26353358Sdim int sd = N - __builtin_clzll(a); // number of significant digits 27353358Sdim int e = sd - 1; // 8 exponent 28353358Sdim if (sd > FLT_MANT_DIG) { 29353358Sdim // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 30353358Sdim // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 31353358Sdim // 12345678901234567890123456 32353358Sdim // 1 = msb 1 bit 33353358Sdim // P = bit FLT_MANT_DIG-1 bits to the right of 1 34353358Sdim // Q = bit FLT_MANT_DIG bits to the right of 1 35353358Sdim // R = "or" of all bits to the right of Q 36353358Sdim switch (sd) { 37353358Sdim case FLT_MANT_DIG + 1: 38353358Sdim a <<= 1; 39353358Sdim break; 40353358Sdim case FLT_MANT_DIG + 2: 41353358Sdim break; 42353358Sdim default: 43353358Sdim a = (a >> (sd - (FLT_MANT_DIG + 2))) | 44353358Sdim ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0); 45353358Sdim }; 46353358Sdim // finish: 47353358Sdim a |= (a & 4) != 0; // Or P into R 48353358Sdim ++a; // round - this step may add a significant bit 49353358Sdim a >>= 2; // dump Q and R 50353358Sdim // a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits 51353358Sdim if (a & ((du_int)1 << FLT_MANT_DIG)) { 52353358Sdim a >>= 1; 53353358Sdim ++e; 54276789Sdim } 55353358Sdim // a is now rounded to FLT_MANT_DIG bits 56353358Sdim } else { 57353358Sdim a <<= (FLT_MANT_DIG - sd); 58353358Sdim // a is now rounded to FLT_MANT_DIG bits 59353358Sdim } 60353358Sdim float_bits fb; 61353358Sdim fb.u = ((e + 127) << 23) | // exponent 62353358Sdim ((su_int)a & 0x007FFFFF); // mantissa 63353358Sdim return fb.f; 64276789Sdim} 65321369Sdim 66321369Sdim#if defined(__ARM_EABI__) 67327952Sdim#if defined(COMPILER_RT_ARMHF_TARGET) 68353358SdimAEABI_RTABI float __aeabi_ul2f(du_int a) { return __floatundisf(a); } 69327952Sdim#else 70353358SdimCOMPILER_RT_ALIAS(__floatundisf, __aeabi_ul2f) 71321369Sdim#endif 72327952Sdim#endif 73