Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame^] | 1 | //===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------===// |
| 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 __mulvsi3 for the compiler_rt library. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
| 14 | #include "int_lib.h" |
| 15 | #include <stdlib.h> |
| 16 | |
| 17 | // Returns: a * b |
| 18 | |
| 19 | // Effects: aborts if a * b overflows |
| 20 | |
| 21 | si_int |
| 22 | __mulvsi3(si_int a, si_int b) |
| 23 | { |
| 24 | const int N = (int)(sizeof(si_int) * CHAR_BIT); |
| 25 | const si_int MIN = (si_int)1 << (N-1); |
| 26 | const si_int MAX = ~MIN; |
| 27 | if (a == MIN) |
| 28 | { |
| 29 | if (b == 0 || b == 1) |
| 30 | return a * b; |
| 31 | abort(); |
| 32 | } |
| 33 | if (b == MIN) |
| 34 | { |
| 35 | if (a == 0 || a == 1) |
| 36 | return a * b; |
| 37 | abort(); |
| 38 | } |
| 39 | si_int sa = a >> (N - 1); |
| 40 | si_int abs_a = (a ^ sa) - sa; |
| 41 | si_int sb = b >> (N - 1); |
| 42 | si_int abs_b = (b ^ sb) - sb; |
| 43 | if (abs_a < 2 || abs_b < 2) |
| 44 | return a * b; |
| 45 | if (sa == sb) |
| 46 | { |
| 47 | if (abs_a > MAX / abs_b) |
| 48 | abort(); |
| 49 | } |
| 50 | else |
| 51 | { |
| 52 | if (abs_a > MIN / -abs_b) |
| 53 | abort(); |
| 54 | } |
| 55 | return a * b; |
| 56 | } |