1*0a6a1f1dSLionel Sambuc /* ===-- floatuntidf.c - Implement __floatuntidf ---------------------------=== 2*0a6a1f1dSLionel Sambuc * 3*0a6a1f1dSLionel Sambuc * The LLVM Compiler Infrastructure 4*0a6a1f1dSLionel Sambuc * 5*0a6a1f1dSLionel Sambuc * This file is dual licensed under the MIT and the University of Illinois Open 6*0a6a1f1dSLionel Sambuc * Source Licenses. See LICENSE.TXT for details. 7*0a6a1f1dSLionel Sambuc * 8*0a6a1f1dSLionel Sambuc * ===----------------------------------------------------------------------=== 9*0a6a1f1dSLionel Sambuc * 10*0a6a1f1dSLionel Sambuc * This file implements __floatuntidf for the compiler_rt library. 11*0a6a1f1dSLionel Sambuc * 12*0a6a1f1dSLionel Sambuc * ===----------------------------------------------------------------------=== 13*0a6a1f1dSLionel Sambuc */ 14*0a6a1f1dSLionel Sambuc 15*0a6a1f1dSLionel Sambuc #include "int_lib.h" 16*0a6a1f1dSLionel Sambuc 17*0a6a1f1dSLionel Sambuc #ifdef CRT_HAS_128BIT 18*0a6a1f1dSLionel Sambuc 19*0a6a1f1dSLionel Sambuc /* Returns: convert a to a double, rounding toward even. */ 20*0a6a1f1dSLionel Sambuc 21*0a6a1f1dSLionel Sambuc /* Assumption: double is a IEEE 64 bit floating point type 22*0a6a1f1dSLionel Sambuc * tu_int is a 128 bit integral type 23*0a6a1f1dSLionel Sambuc */ 24*0a6a1f1dSLionel Sambuc 25*0a6a1f1dSLionel Sambuc /* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */ 26*0a6a1f1dSLionel Sambuc 27*0a6a1f1dSLionel Sambuc COMPILER_RT_ABI double __floatuntidf(tu_int a)28*0a6a1f1dSLionel Sambuc__floatuntidf(tu_int a) 29*0a6a1f1dSLionel Sambuc { 30*0a6a1f1dSLionel Sambuc if (a == 0) 31*0a6a1f1dSLionel Sambuc return 0.0; 32*0a6a1f1dSLionel Sambuc const unsigned N = sizeof(tu_int) * CHAR_BIT; 33*0a6a1f1dSLionel Sambuc int sd = N - __clzti2(a); /* number of significant digits */ 34*0a6a1f1dSLionel Sambuc int e = sd - 1; /* exponent */ 35*0a6a1f1dSLionel Sambuc if (sd > DBL_MANT_DIG) 36*0a6a1f1dSLionel Sambuc { 37*0a6a1f1dSLionel Sambuc /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 38*0a6a1f1dSLionel Sambuc * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 39*0a6a1f1dSLionel Sambuc * 12345678901234567890123456 40*0a6a1f1dSLionel Sambuc * 1 = msb 1 bit 41*0a6a1f1dSLionel Sambuc * P = bit DBL_MANT_DIG-1 bits to the right of 1 42*0a6a1f1dSLionel Sambuc * Q = bit DBL_MANT_DIG bits to the right of 1 43*0a6a1f1dSLionel Sambuc * R = "or" of all bits to the right of Q 44*0a6a1f1dSLionel Sambuc */ 45*0a6a1f1dSLionel Sambuc switch (sd) 46*0a6a1f1dSLionel Sambuc { 47*0a6a1f1dSLionel Sambuc case DBL_MANT_DIG + 1: 48*0a6a1f1dSLionel Sambuc a <<= 1; 49*0a6a1f1dSLionel Sambuc break; 50*0a6a1f1dSLionel Sambuc case DBL_MANT_DIG + 2: 51*0a6a1f1dSLionel Sambuc break; 52*0a6a1f1dSLionel Sambuc default: 53*0a6a1f1dSLionel Sambuc a = (a >> (sd - (DBL_MANT_DIG+2))) | 54*0a6a1f1dSLionel Sambuc ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG+2) - sd))) != 0); 55*0a6a1f1dSLionel Sambuc }; 56*0a6a1f1dSLionel Sambuc /* finish: */ 57*0a6a1f1dSLionel Sambuc a |= (a & 4) != 0; /* Or P into R */ 58*0a6a1f1dSLionel Sambuc ++a; /* round - this step may add a significant bit */ 59*0a6a1f1dSLionel Sambuc a >>= 2; /* dump Q and R */ 60*0a6a1f1dSLionel Sambuc /* a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits */ 61*0a6a1f1dSLionel Sambuc if (a & ((tu_int)1 << DBL_MANT_DIG)) 62*0a6a1f1dSLionel Sambuc { 63*0a6a1f1dSLionel Sambuc a >>= 1; 64*0a6a1f1dSLionel Sambuc ++e; 65*0a6a1f1dSLionel Sambuc } 66*0a6a1f1dSLionel Sambuc /* a is now rounded to DBL_MANT_DIG bits */ 67*0a6a1f1dSLionel Sambuc } 68*0a6a1f1dSLionel Sambuc else 69*0a6a1f1dSLionel Sambuc { 70*0a6a1f1dSLionel Sambuc a <<= (DBL_MANT_DIG - sd); 71*0a6a1f1dSLionel Sambuc /* a is now rounded to DBL_MANT_DIG bits */ 72*0a6a1f1dSLionel Sambuc } 73*0a6a1f1dSLionel Sambuc double_bits fb; 74*0a6a1f1dSLionel Sambuc fb.u.s.high = ((e + 1023) << 20) | /* exponent */ 75*0a6a1f1dSLionel Sambuc ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */ 76*0a6a1f1dSLionel Sambuc fb.u.s.low = (su_int)a; /* mantissa-low */ 77*0a6a1f1dSLionel Sambuc return fb.f; 78*0a6a1f1dSLionel Sambuc } 79*0a6a1f1dSLionel Sambuc 80*0a6a1f1dSLionel Sambuc #endif /* CRT_HAS_128BIT */ 81