1*0a6a1f1dSLionel Sambuc /*===-- floatdisf.c - Implement __floatdisf -------------------------------=== 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 __floatdisf for the compiler_rt library. 11*0a6a1f1dSLionel Sambuc * 12*0a6a1f1dSLionel Sambuc *===----------------------------------------------------------------------=== 13*0a6a1f1dSLionel Sambuc */ 14*0a6a1f1dSLionel Sambuc 15*0a6a1f1dSLionel Sambuc /* Returns: convert a to a float, rounding toward even.*/ 16*0a6a1f1dSLionel Sambuc 17*0a6a1f1dSLionel Sambuc /* Assumption: float is a IEEE 32 bit floating point type 18*0a6a1f1dSLionel Sambuc * di_int is a 64 bit integral type 19*0a6a1f1dSLionel Sambuc */ 20*0a6a1f1dSLionel Sambuc 21*0a6a1f1dSLionel Sambuc /* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */ 22*0a6a1f1dSLionel Sambuc 23*0a6a1f1dSLionel Sambuc #include "int_lib.h" 24*0a6a1f1dSLionel Sambuc ARM_EABI_FNALIAS(l2f,floatdisf)25*0a6a1f1dSLionel SambucARM_EABI_FNALIAS(l2f, floatdisf) 26*0a6a1f1dSLionel Sambuc 27*0a6a1f1dSLionel Sambuc COMPILER_RT_ABI float 28*0a6a1f1dSLionel Sambuc __floatdisf(di_int a) 29*0a6a1f1dSLionel Sambuc { 30*0a6a1f1dSLionel Sambuc if (a == 0) 31*0a6a1f1dSLionel Sambuc return 0.0F; 32*0a6a1f1dSLionel Sambuc const unsigned N = sizeof(di_int) * CHAR_BIT; 33*0a6a1f1dSLionel Sambuc const di_int s = a >> (N-1); 34*0a6a1f1dSLionel Sambuc a = (a ^ s) - s; 35*0a6a1f1dSLionel Sambuc int sd = N - __builtin_clzll(a); /* number of significant digits */ 36*0a6a1f1dSLionel Sambuc int e = sd - 1; /* exponent */ 37*0a6a1f1dSLionel Sambuc if (sd > FLT_MANT_DIG) 38*0a6a1f1dSLionel Sambuc { 39*0a6a1f1dSLionel Sambuc /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 40*0a6a1f1dSLionel Sambuc * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 41*0a6a1f1dSLionel Sambuc * 12345678901234567890123456 42*0a6a1f1dSLionel Sambuc * 1 = msb 1 bit 43*0a6a1f1dSLionel Sambuc * P = bit FLT_MANT_DIG-1 bits to the right of 1 44*0a6a1f1dSLionel Sambuc * Q = bit FLT_MANT_DIG bits to the right of 1 45*0a6a1f1dSLionel Sambuc * R = "or" of all bits to the right of Q 46*0a6a1f1dSLionel Sambuc */ 47*0a6a1f1dSLionel Sambuc switch (sd) 48*0a6a1f1dSLionel Sambuc { 49*0a6a1f1dSLionel Sambuc case FLT_MANT_DIG + 1: 50*0a6a1f1dSLionel Sambuc a <<= 1; 51*0a6a1f1dSLionel Sambuc break; 52*0a6a1f1dSLionel Sambuc case FLT_MANT_DIG + 2: 53*0a6a1f1dSLionel Sambuc break; 54*0a6a1f1dSLionel Sambuc default: 55*0a6a1f1dSLionel Sambuc a = ((du_int)a >> (sd - (FLT_MANT_DIG+2))) | 56*0a6a1f1dSLionel Sambuc ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0); 57*0a6a1f1dSLionel Sambuc }; 58*0a6a1f1dSLionel Sambuc /* finish: */ 59*0a6a1f1dSLionel Sambuc a |= (a & 4) != 0; /* Or P into R */ 60*0a6a1f1dSLionel Sambuc ++a; /* round - this step may add a significant bit */ 61*0a6a1f1dSLionel Sambuc a >>= 2; /* dump Q and R */ 62*0a6a1f1dSLionel Sambuc /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */ 63*0a6a1f1dSLionel Sambuc if (a & ((du_int)1 << FLT_MANT_DIG)) 64*0a6a1f1dSLionel Sambuc { 65*0a6a1f1dSLionel Sambuc a >>= 1; 66*0a6a1f1dSLionel Sambuc ++e; 67*0a6a1f1dSLionel Sambuc } 68*0a6a1f1dSLionel Sambuc /* a is now rounded to FLT_MANT_DIG bits */ 69*0a6a1f1dSLionel Sambuc } 70*0a6a1f1dSLionel Sambuc else 71*0a6a1f1dSLionel Sambuc { 72*0a6a1f1dSLionel Sambuc a <<= (FLT_MANT_DIG - sd); 73*0a6a1f1dSLionel Sambuc /* a is now rounded to FLT_MANT_DIG bits */ 74*0a6a1f1dSLionel Sambuc } 75*0a6a1f1dSLionel Sambuc float_bits fb; 76*0a6a1f1dSLionel Sambuc fb.u = ((su_int)s & 0x80000000) | /* sign */ 77*0a6a1f1dSLionel Sambuc ((e + 127) << 23) | /* exponent */ 78*0a6a1f1dSLionel Sambuc ((su_int)a & 0x007FFFFF); /* mantissa */ 79*0a6a1f1dSLionel Sambuc return fb.f; 80*0a6a1f1dSLionel Sambuc } 81