Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 1 | /* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------=== |
| 2 | * |
| 3 | * The LLVM Compiler Infrastructure |
| 4 | * |
| 5 | * This file is distributed under the University of Illinois Open Source |
| 6 | * License. See LICENSE.TXT for details. |
| 7 | * |
| 8 | * ===----------------------------------------------------------------------=== |
| 9 | * |
| 10 | * This file implements __udivsi3 for the compiler_rt library. |
| 11 | * |
| 12 | * ===----------------------------------------------------------------------=== |
| 13 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 14 | |
| 15 | #include "int_lib.h" |
| 16 | |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 17 | /* Returns: a / b */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 18 | |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 19 | /* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 20 | |
| 21 | su_int |
| 22 | __udivsi3(su_int n, su_int d) |
| 23 | { |
| 24 | const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT; |
| 25 | su_int q; |
| 26 | su_int r; |
| 27 | unsigned sr; |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 28 | /* special cases */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 29 | if (d == 0) |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 30 | return 0; /* ?! */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 31 | if (n == 0) |
| 32 | return 0; |
| 33 | sr = __builtin_clz(d) - __builtin_clz(n); |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 34 | /* 0 <= sr <= n_uword_bits - 1 or sr large */ |
| 35 | if (sr > n_uword_bits - 1) /* d > r */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 36 | return 0; |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 37 | if (sr == n_uword_bits - 1) /* d == 1 */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 38 | return n; |
| 39 | ++sr; |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 40 | /* 1 <= sr <= n_uword_bits - 1 */ |
| 41 | /* Not a special case */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 42 | q = n << (n_uword_bits - sr); |
| 43 | r = n >> sr; |
| 44 | su_int carry = 0; |
| 45 | for (; sr > 0; --sr) |
| 46 | { |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 47 | /* r:q = ((r:q) << 1) | carry */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 48 | r = (r << 1) | (q >> (n_uword_bits - 1)); |
| 49 | q = (q << 1) | carry; |
Edward O'Callaghan | 37a6a45 | 2009-08-07 20:30:09 +0000 | [diff] [blame^] | 50 | /* carry = 0; |
| 51 | * if (r.all >= d.all) |
| 52 | * { |
| 53 | * r.all -= d.all; |
| 54 | * carry = 1; |
| 55 | * } |
| 56 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 57 | const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1); |
| 58 | carry = s & 1; |
| 59 | r -= d & s; |
| 60 | } |
| 61 | q = (q << 1) | carry; |
| 62 | return q; |
| 63 | } |