1 //===-- floatundisf.c - Implement __floatundisf ---------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements __floatundisf for the compiler_rt library. 10 // 11 //===----------------------------------------------------------------------===// 12 13 // Returns: convert a to a float, rounding toward even. 14 15 // Assumption: float is a IEEE 32 bit floating point type 16 // du_int is a 64 bit integral type 17 18 // seee eeee emmm mmmm mmmm mmmm mmmm mmmm 19 20 #include "int_lib.h" 21 22 COMPILER_RT_ABI float __floatundisf(du_int a) { 23 if (a == 0) 24 return 0.0F; 25 const unsigned N = sizeof(du_int) * CHAR_BIT; 26 int sd = N - __builtin_clzll(a); // number of significant digits 27 si_int e = sd - 1; // 8 exponent 28 if (sd > FLT_MANT_DIG) { 29 // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 30 // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 31 // 12345678901234567890123456 32 // 1 = msb 1 bit 33 // P = bit FLT_MANT_DIG-1 bits to the right of 1 34 // Q = bit FLT_MANT_DIG bits to the right of 1 35 // R = "or" of all bits to the right of Q 36 switch (sd) { 37 case FLT_MANT_DIG + 1: 38 a <<= 1; 39 break; 40 case FLT_MANT_DIG + 2: 41 break; 42 default: 43 a = (a >> (sd - (FLT_MANT_DIG + 2))) | 44 ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0); 45 }; 46 // finish: 47 a |= (a & 4) != 0; // Or P into R 48 ++a; // round - this step may add a significant bit 49 a >>= 2; // dump Q and R 50 // a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits 51 if (a & ((du_int)1 << FLT_MANT_DIG)) { 52 a >>= 1; 53 ++e; 54 } 55 // a is now rounded to FLT_MANT_DIG bits 56 } else { 57 a <<= (FLT_MANT_DIG - sd); 58 // a is now rounded to FLT_MANT_DIG bits 59 } 60 float_bits fb; 61 fb.u = ((e + 127) << 23) | // exponent 62 ((su_int)a & 0x007FFFFF); // mantissa 63 return fb.f; 64 } 65 66 #if defined(__ARM_EABI__) 67 #if defined(COMPILER_RT_ARMHF_TARGET) 68 AEABI_RTABI float __aeabi_ul2f(du_int a) { return __floatundisf(a); } 69 #else 70 COMPILER_RT_ALIAS(__floatundisf, __aeabi_ul2f) 71 #endif 72 #endif 73