1*3cab2bb3Spatrick //===-- floatundisf.c - Implement __floatundisf ---------------------------===// 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 __floatundisf for the compiler_rt library. 10*3cab2bb3Spatrick // 11*3cab2bb3Spatrick //===----------------------------------------------------------------------===// 12*3cab2bb3Spatrick 13*3cab2bb3Spatrick // Returns: convert a to a float, rounding toward even. 14*3cab2bb3Spatrick 15*3cab2bb3Spatrick // Assumption: float is a IEEE 32 bit floating point type 16*3cab2bb3Spatrick // du_int is a 64 bit integral type 17*3cab2bb3Spatrick 18*3cab2bb3Spatrick // seee eeee emmm mmmm mmmm mmmm mmmm mmmm 19*3cab2bb3Spatrick 20*3cab2bb3Spatrick #include "int_lib.h" 21*3cab2bb3Spatrick 22*3cab2bb3Spatrick COMPILER_RT_ABI float __floatundisf(du_int a) { 23*3cab2bb3Spatrick if (a == 0) 24*3cab2bb3Spatrick return 0.0F; 25*3cab2bb3Spatrick const unsigned N = sizeof(du_int) * CHAR_BIT; 26*3cab2bb3Spatrick int sd = N - __builtin_clzll(a); // number of significant digits 27*3cab2bb3Spatrick int e = sd - 1; // 8 exponent 28*3cab2bb3Spatrick if (sd > FLT_MANT_DIG) { 29*3cab2bb3Spatrick // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 30*3cab2bb3Spatrick // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 31*3cab2bb3Spatrick // 12345678901234567890123456 32*3cab2bb3Spatrick // 1 = msb 1 bit 33*3cab2bb3Spatrick // P = bit FLT_MANT_DIG-1 bits to the right of 1 34*3cab2bb3Spatrick // Q = bit FLT_MANT_DIG bits to the right of 1 35*3cab2bb3Spatrick // R = "or" of all bits to the right of Q 36*3cab2bb3Spatrick switch (sd) { 37*3cab2bb3Spatrick case FLT_MANT_DIG + 1: 38*3cab2bb3Spatrick a <<= 1; 39*3cab2bb3Spatrick break; 40*3cab2bb3Spatrick case FLT_MANT_DIG + 2: 41*3cab2bb3Spatrick break; 42*3cab2bb3Spatrick default: 43*3cab2bb3Spatrick a = (a >> (sd - (FLT_MANT_DIG + 2))) | 44*3cab2bb3Spatrick ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0); 45*3cab2bb3Spatrick }; 46*3cab2bb3Spatrick // finish: 47*3cab2bb3Spatrick a |= (a & 4) != 0; // Or P into R 48*3cab2bb3Spatrick ++a; // round - this step may add a significant bit 49*3cab2bb3Spatrick a >>= 2; // dump Q and R 50*3cab2bb3Spatrick // a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits 51*3cab2bb3Spatrick if (a & ((du_int)1 << FLT_MANT_DIG)) { 52*3cab2bb3Spatrick a >>= 1; 53*3cab2bb3Spatrick ++e; 54*3cab2bb3Spatrick } 55*3cab2bb3Spatrick // a is now rounded to FLT_MANT_DIG bits 56*3cab2bb3Spatrick } else { 57*3cab2bb3Spatrick a <<= (FLT_MANT_DIG - sd); 58*3cab2bb3Spatrick // a is now rounded to FLT_MANT_DIG bits 59*3cab2bb3Spatrick } 60*3cab2bb3Spatrick float_bits fb; 61*3cab2bb3Spatrick fb.u = ((e + 127) << 23) | // exponent 62*3cab2bb3Spatrick ((su_int)a & 0x007FFFFF); // mantissa 63*3cab2bb3Spatrick return fb.f; 64*3cab2bb3Spatrick } 65*3cab2bb3Spatrick 66*3cab2bb3Spatrick #if defined(__ARM_EABI__) 67*3cab2bb3Spatrick #if defined(COMPILER_RT_ARMHF_TARGET) 68*3cab2bb3Spatrick AEABI_RTABI float __aeabi_ul2f(du_int a) { return __floatundisf(a); } 69*3cab2bb3Spatrick #else 70*3cab2bb3Spatrick COMPILER_RT_ALIAS(__floatundisf, __aeabi_ul2f) 71*3cab2bb3Spatrick #endif 72*3cab2bb3Spatrick #endif 73