1214152Sed/*===-- floatdisf.c - Implement __floatdisf -------------------------------=== 2214152Sed * 3214152Sed * The LLVM Compiler Infrastructure 4214152Sed * 5222656Sed * This file is dual licensed under the MIT and the University of Illinois Open 6222656Sed * Source Licenses. See LICENSE.TXT for details. 7214152Sed * 8214152Sed *===----------------------------------------------------------------------=== 9214152Sed * 10214152Sed * This file implements __floatdisf for the compiler_rt library. 11214152Sed * 12214152Sed *===----------------------------------------------------------------------=== 13214152Sed */ 14214152Sed 15214152Sed/* Returns: convert a to a float, rounding toward even.*/ 16214152Sed 17214152Sed/* Assumption: float is a IEEE 32 bit floating point type 18214152Sed * di_int is a 64 bit integral type 19214152Sed */ 20214152Sed 21214152Sed/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */ 22214152Sed 23222656Sed#include "int_lib.h" 24222656Sed 25239138SandrewARM_EABI_FNALIAS(l2f, floatdisf) 26222656Sed 27222656SedCOMPILER_RT_ABI float 28214152Sed__floatdisf(di_int a) 29214152Sed{ 30214152Sed if (a == 0) 31214152Sed return 0.0F; 32214152Sed const unsigned N = sizeof(di_int) * CHAR_BIT; 33214152Sed const di_int s = a >> (N-1); 34214152Sed a = (a ^ s) - s; 35214152Sed int sd = N - __builtin_clzll(a); /* number of significant digits */ 36214152Sed int e = sd - 1; /* exponent */ 37214152Sed if (sd > FLT_MANT_DIG) 38214152Sed { 39214152Sed /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 40214152Sed * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 41214152Sed * 12345678901234567890123456 42214152Sed * 1 = msb 1 bit 43214152Sed * P = bit FLT_MANT_DIG-1 bits to the right of 1 44214152Sed * Q = bit FLT_MANT_DIG bits to the right of 1 45214152Sed * R = "or" of all bits to the right of Q 46214152Sed */ 47214152Sed switch (sd) 48214152Sed { 49214152Sed case FLT_MANT_DIG + 1: 50214152Sed a <<= 1; 51214152Sed break; 52214152Sed case FLT_MANT_DIG + 2: 53214152Sed break; 54214152Sed default: 55214152Sed a = ((du_int)a >> (sd - (FLT_MANT_DIG+2))) | 56214152Sed ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0); 57214152Sed }; 58214152Sed /* finish: */ 59214152Sed a |= (a & 4) != 0; /* Or P into R */ 60214152Sed ++a; /* round - this step may add a significant bit */ 61214152Sed a >>= 2; /* dump Q and R */ 62214152Sed /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */ 63214152Sed if (a & ((du_int)1 << FLT_MANT_DIG)) 64214152Sed { 65214152Sed a >>= 1; 66214152Sed ++e; 67214152Sed } 68214152Sed /* a is now rounded to FLT_MANT_DIG bits */ 69214152Sed } 70214152Sed else 71214152Sed { 72214152Sed a <<= (FLT_MANT_DIG - sd); 73214152Sed /* a is now rounded to FLT_MANT_DIG bits */ 74214152Sed } 75214152Sed float_bits fb; 76214152Sed fb.u = ((su_int)s & 0x80000000) | /* sign */ 77214152Sed ((e + 127) << 23) | /* exponent */ 78214152Sed ((su_int)a & 0x007FFFFF); /* mantissa */ 79214152Sed return fb.f; 80214152Sed} 81