1214152Sed/* ===-- floattisf.c - Implement __floattisf -------------------------------=== 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 __floattisf for the compiler_rt library. 11214152Sed * 12214152Sed * ===----------------------------------------------------------------------=== 13214152Sed */ 14214152Sed 15263560Sdim#include "int_lib.h" 16263560Sdim 17263764Sdim#ifdef CRT_HAS_128BIT 18214152Sed 19214152Sed/* Returns: convert a to a float, rounding toward even. */ 20214152Sed 21214152Sed/* Assumption: float is a IEEE 32 bit floating point type 22214152Sed * ti_int is a 128 bit integral type 23214152Sed */ 24214152Sed 25214152Sed/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */ 26214152Sed 27214152Sedsi_int __clzti2(ti_int a); 28214152Sed 29214152Sedfloat 30214152Sed__floattisf(ti_int a) 31214152Sed{ 32214152Sed if (a == 0) 33214152Sed return 0.0F; 34214152Sed const unsigned N = sizeof(ti_int) * CHAR_BIT; 35214152Sed const ti_int s = a >> (N-1); 36214152Sed a = (a ^ s) - s; 37214152Sed int sd = N - __clzti2(a); /* number of significant digits */ 38214152Sed int e = sd - 1; /* exponent */ 39214152Sed if (sd > FLT_MANT_DIG) 40214152Sed { 41214152Sed /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 42214152Sed * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 43214152Sed * 12345678901234567890123456 44214152Sed * 1 = msb 1 bit 45214152Sed * P = bit FLT_MANT_DIG-1 bits to the right of 1 46214152Sed * Q = bit FLT_MANT_DIG bits to the right of 1 47214152Sed * R = "or" of all bits to the right of Q 48214152Sed */ 49214152Sed switch (sd) 50214152Sed { 51214152Sed case FLT_MANT_DIG + 1: 52214152Sed a <<= 1; 53214152Sed break; 54214152Sed case FLT_MANT_DIG + 2: 55214152Sed break; 56214152Sed default: 57214152Sed a = ((tu_int)a >> (sd - (FLT_MANT_DIG+2))) | 58214152Sed ((a & ((tu_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0); 59214152Sed }; 60214152Sed /* finish: */ 61214152Sed a |= (a & 4) != 0; /* Or P into R */ 62214152Sed ++a; /* round - this step may add a significant bit */ 63214152Sed a >>= 2; /* dump Q and R */ 64214152Sed /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */ 65214152Sed if (a & ((tu_int)1 << FLT_MANT_DIG)) 66214152Sed { 67214152Sed a >>= 1; 68214152Sed ++e; 69214152Sed } 70214152Sed /* a is now rounded to FLT_MANT_DIG bits */ 71214152Sed } 72214152Sed else 73214152Sed { 74214152Sed a <<= (FLT_MANT_DIG - sd); 75214152Sed /* a is now rounded to FLT_MANT_DIG bits */ 76214152Sed } 77214152Sed float_bits fb; 78214152Sed fb.u = ((su_int)s & 0x80000000) | /* sign */ 79214152Sed ((e + 127) << 23) | /* exponent */ 80214152Sed ((su_int)a & 0x007FFFFF); /* mantissa */ 81214152Sed return fb.f; 82214152Sed} 83214152Sed 84263764Sdim#endif /* CRT_HAS_128BIT */ 85