1 /*===-- floatdisf.c - Implement __floatdisf -------------------------------===
3 * The LLVM Compiler Infrastructure
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
8 *===----------------------------------------------------------------------===
10 * This file implements __floatdisf for the compiler_rt library.
12 *===----------------------------------------------------------------------===
18 /* Returns: convert a to a float, rounding toward even.*/
20 /* Assumption: float is a IEEE 32 bit floating point type
21 * di_int is a 64 bit integral type
24 /* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */
28 ARM_EABI_FNALIAS(l2f, floatdisf);
35 const unsigned N = sizeof(di_int) * CHAR_BIT;
36 const di_int s = a >> (N-1);
38 int sd = N - __builtin_clzll(a); /* number of significant digits */
39 int e = sd - 1; /* exponent */
40 if (sd > FLT_MANT_DIG)
42 /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
43 * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
44 * 12345678901234567890123456
46 * P = bit FLT_MANT_DIG-1 bits to the right of 1
47 * Q = bit FLT_MANT_DIG bits to the right of 1
48 * R = "or" of all bits to the right of Q
52 case FLT_MANT_DIG + 1:
55 case FLT_MANT_DIG + 2:
58 a = ((du_int)a >> (sd - (FLT_MANT_DIG+2))) |
59 ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0);
62 a |= (a & 4) != 0; /* Or P into R */
63 ++a; /* round - this step may add a significant bit */
64 a >>= 2; /* dump Q and R */
65 /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */
66 if (a & ((du_int)1 << FLT_MANT_DIG))
71 /* a is now rounded to FLT_MANT_DIG bits */
75 a <<= (FLT_MANT_DIG - sd);
76 /* a is now rounded to FLT_MANT_DIG bits */
79 fb.u = ((su_int)s & 0x80000000) | /* sign */
80 ((e + 127) << 23) | /* exponent */
81 ((su_int)a & 0x007FFFFF); /* mantissa */