Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 1 | /* ===-- floattixf.c - Implement __floattixf -------------------------------=== |
| 2 | * |
| 3 | * The LLVM Compiler Infrastructure |
| 4 | * |
Howard Hinnant | 9ad441f | 2010-11-16 22:13:33 +0000 | [diff] [blame] | 5 | * This file is dual licensed under the MIT and the University of Illinois Open |
| 6 | * Source Licenses. See LICENSE.TXT for details. |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 7 | * |
| 8 | * ===----------------------------------------------------------------------=== |
| 9 | * |
| 10 | * This file implements __floattixf for the compiler_rt library. |
| 11 | * |
| 12 | * ===----------------------------------------------------------------------=== |
| 13 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 14 | |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 15 | #include "int_lib.h" |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 16 | |
Chandler Carruth | 7f2d7c7 | 2012-06-22 21:09:22 +0000 | [diff] [blame^] | 17 | #if __x86_64 |
| 18 | |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 19 | /* Returns: convert a to a long double, rounding toward even. */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 20 | |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 21 | /* Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits |
| 22 | * ti_int is a 128 bit integral type |
| 23 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 24 | |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 25 | /* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee | |
| 26 | * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm |
| 27 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 28 | |
| 29 | si_int __clzti2(ti_int a); |
| 30 | |
| 31 | long double |
| 32 | __floattixf(ti_int a) |
| 33 | { |
| 34 | if (a == 0) |
| 35 | return 0.0; |
| 36 | const unsigned N = sizeof(ti_int) * CHAR_BIT; |
| 37 | const ti_int s = a >> (N-1); |
| 38 | a = (a ^ s) - s; |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame] | 39 | int sd = N - __clzti2(a); /* number of significant digits */ |
| 40 | int e = sd - 1; /* exponent */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 41 | if (sd > LDBL_MANT_DIG) |
| 42 | { |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 43 | /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx |
| 44 | * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR |
| 45 | * 12345678901234567890123456 |
| 46 | * 1 = msb 1 bit |
| 47 | * P = bit LDBL_MANT_DIG-1 bits to the right of 1 |
| 48 | * Q = bit LDBL_MANT_DIG bits to the right of 1 |
| 49 | * R = "or" of all bits to the right of Q |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame] | 50 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 51 | switch (sd) |
| 52 | { |
| 53 | case LDBL_MANT_DIG + 1: |
| 54 | a <<= 1; |
| 55 | break; |
| 56 | case LDBL_MANT_DIG + 2: |
| 57 | break; |
| 58 | default: |
| 59 | a = ((tu_int)a >> (sd - (LDBL_MANT_DIG+2))) | |
| 60 | ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG+2) - sd))) != 0); |
| 61 | }; |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 62 | /* finish: */ |
| 63 | a |= (a & 4) != 0; /* Or P into R */ |
| 64 | ++a; /* round - this step may add a significant bit */ |
| 65 | a >>= 2; /* dump Q and R */ |
| 66 | /* a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 67 | if (a & ((tu_int)1 << LDBL_MANT_DIG)) |
| 68 | { |
| 69 | a >>= 1; |
| 70 | ++e; |
| 71 | } |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 72 | /* a is now rounded to LDBL_MANT_DIG bits */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 73 | } |
| 74 | else |
| 75 | { |
| 76 | a <<= (LDBL_MANT_DIG - sd); |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 77 | /* a is now rounded to LDBL_MANT_DIG bits */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 78 | } |
| 79 | long_double_bits fb; |
Edward O'Callaghan | aabd961 | 2009-09-03 09:12:20 +0000 | [diff] [blame] | 80 | fb.u.high.s.low = ((su_int)s & 0x8000) | /* sign */ |
Edward O'Callaghan | 2bf6272 | 2009-08-05 04:02:56 +0000 | [diff] [blame] | 81 | (e + 16383); /* exponent */ |
| 82 | fb.u.low.all = (du_int)a; /* mantissa */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 83 | return fb.f; |
| 84 | } |
| 85 | |
| 86 | #endif |