177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao/* ===-- floatuntidf.c - Implement __floatuntidf ---------------------------=== 277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * The LLVM Compiler Infrastructure 477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * This file is distributed under the University of Illinois Open Source 677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * License. See LICENSE.TXT for details. 777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * ===----------------------------------------------------------------------=== 977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 1077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * This file implements __floatuntidf for the compiler_rt library. 1177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 1277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * ===----------------------------------------------------------------------=== 1377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao */ 1477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 1577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao#if __x86_64 1677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 1777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao#include "int_lib.h" 1877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao#include <float.h> 1977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 2077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao/* Returns: convert a to a double, rounding toward even. */ 2177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 2277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao/* Assumption: double is a IEEE 64 bit floating point type 2377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * tu_int is a 128 bit integral type 2477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao */ 2577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 2677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */ 2777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 2877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liaosi_int __clzti2(ti_int a); 2977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 3077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liaodouble 3177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao__floatuntidf(tu_int a) 3277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao{ 3377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao if (a == 0) 3477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao return 0.0; 3577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao const unsigned N = sizeof(tu_int) * CHAR_BIT; 3677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao int sd = N - __clzti2(a); /* number of significant digits */ 3777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao int e = sd - 1; /* exponent */ 3877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao if (sd > DBL_MANT_DIG) 3977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao { 4077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 4177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 4277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 12345678901234567890123456 4377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * 1 = msb 1 bit 4477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * P = bit DBL_MANT_DIG-1 bits to the right of 1 4577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * Q = bit DBL_MANT_DIG bits to the right of 1 4677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao * R = "or" of all bits to the right of Q 4777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao */ 4877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao switch (sd) 4977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao { 5077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao case DBL_MANT_DIG + 1: 5177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a <<= 1; 5277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao break; 5377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao case DBL_MANT_DIG + 2: 5477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao break; 5577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao default: 5677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a = (a >> (sd - (DBL_MANT_DIG+2))) | 5777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG+2) - sd))) != 0); 5877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao }; 5977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao /* finish: */ 6077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a |= (a & 4) != 0; /* Or P into R */ 6177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao ++a; /* round - this step may add a significant bit */ 6277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a >>= 2; /* dump Q and R */ 6377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao /* a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits */ 6477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao if (a & ((tu_int)1 << DBL_MANT_DIG)) 6577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao { 6677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a >>= 1; 6777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao ++e; 6877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao } 6977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao /* a is now rounded to DBL_MANT_DIG bits */ 7077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao } 7177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao else 7277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao { 7377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao a <<= (DBL_MANT_DIG - sd); 7477ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao /* a is now rounded to DBL_MANT_DIG bits */ 7577ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao } 7677ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao double_bits fb; 7777ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao fb.u.s.high = ((e + 1023) << 20) | /* exponent */ 7877ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */ 7977ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao fb.u.s.low = (su_int)a; /* mantissa-low */ 8077ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao return fb.f; 8177ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao} 8277ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao 8377ed6142daed1e068fbda64405d0de9845e40e1Shih-wei Liao#endif 84