11fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan/* ===-- floatuntisf.c - Implement __floatuntisf ---------------------------=== 21fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 31fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * The LLVM Compiler Infrastructure 41fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 59ad441ffec97db647fee3725b3424284fb913e14Howard Hinnant * This file is dual licensed under the MIT and the University of Illinois Open 69ad441ffec97db647fee3725b3424284fb913e14Howard Hinnant * Source Licenses. See LICENSE.TXT for details. 71fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 81fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * ===----------------------------------------------------------------------=== 91fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 101fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * This file implements __floatuntisf for the compiler_rt library. 111fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 121fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * ===----------------------------------------------------------------------=== 131fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan */ 14b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 15b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar#include "int_lib.h" 16b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 172d1fdb26e458c4ddc04155c1d421bced3ba90cd0Stephen Hines#ifdef CRT_HAS_128BIT 187f2d7c75e713d778106d01a54e7aef40227bbf2dChandler Carruth 191fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan/* Returns: convert a to a float, rounding toward even. */ 20b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 211fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan/* Assumption: float is a IEEE 32 bit floating point type 221fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * tu_int is a 128 bit integral type 231fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan */ 24b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 251fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */ 26b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 272d1fdb26e458c4ddc04155c1d421bced3ba90cd0Stephen HinesCOMPILER_RT_ABI float 28b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar__floatuntisf(tu_int a) 29b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar{ 30b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar if (a == 0) 31b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return 0.0F; 32b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const unsigned N = sizeof(tu_int) * CHAR_BIT; 331fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan int sd = N - __clzti2(a); /* number of significant digits */ 341fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan int e = sd - 1; /* exponent */ 35b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar if (sd > FLT_MANT_DIG) 36b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 371fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 381fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 391fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 12345678901234567890123456 401fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * 1 = msb 1 bit 411fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * P = bit FLT_MANT_DIG-1 bits to the right of 1 421fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * Q = bit FLT_MANT_DIG bits to the right of 1 431fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan * R = "or" of all bits to the right of Q 441fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan */ 45b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar switch (sd) 46b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 47b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar case FLT_MANT_DIG + 1: 48b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar a <<= 1; 49b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar break; 50b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar case FLT_MANT_DIG + 2: 51b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar break; 52b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar default: 53b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar a = (a >> (sd - (FLT_MANT_DIG+2))) | 54b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar ((a & ((tu_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0); 55b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar }; 561fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan /* finish: */ 571fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan a |= (a & 4) != 0; /* Or P into R */ 581fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan ++a; /* round - this step may add a significant bit */ 591fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan a >>= 2; /* dump Q and R */ 601fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */ 61b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar if (a & ((tu_int)1 << FLT_MANT_DIG)) 62b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 63b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar a >>= 1; 64b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar ++e; 65b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar } 661fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan /* a is now rounded to FLT_MANT_DIG bits */ 67b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar } 68b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar else 69b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 70b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar a <<= (FLT_MANT_DIG - sd); 711fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan /* a is now rounded to FLT_MANT_DIG bits */ 72b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar } 73b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar float_bits fb; 741fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan fb.u = ((e + 127) << 23) | /* exponent */ 751fcb40b79d8fbfcc9acb0966d5f9bba09431f832Edward O'Callaghan ((su_int)a & 0x007FFFFF); /* mantissa */ 76b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return fb.f; 77b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar} 78b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 792d1fdb26e458c4ddc04155c1d421bced3ba90cd0Stephen Hines#endif /* CRT_HAS_128BIT */ 80