Edward O'Callaghan | 1fcb40b | 2009-08-05 19:06:50 +0000 | [diff] [blame] | 1 | /* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------=== |
| 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 | 1fcb40b | 2009-08-05 19:06:50 +0000 | [diff] [blame] | 7 | * |
| 8 | * ===----------------------------------------------------------------------=== |
| 9 | * |
| 10 | * This file implements __mulvti3 for the compiler_rt library. |
| 11 | * |
| 12 | * ===----------------------------------------------------------------------=== |
| 13 | */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 14 | |
| 15 | #if __x86_64 |
| 16 | |
| 17 | #include "int_lib.h" |
| 18 | #include <stdlib.h> |
| 19 | |
Edward O'Callaghan | 1fcb40b | 2009-08-05 19:06:50 +0000 | [diff] [blame] | 20 | /* Returns: a * b */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 21 | |
Edward O'Callaghan | 1fcb40b | 2009-08-05 19:06:50 +0000 | [diff] [blame] | 22 | /* Effects: aborts if a * b overflows */ |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 23 | |
| 24 | ti_int |
| 25 | __mulvti3(ti_int a, ti_int b) |
| 26 | { |
| 27 | const int N = (int)(sizeof(ti_int) * CHAR_BIT); |
| 28 | const ti_int MIN = (ti_int)1 << (N-1); |
| 29 | const ti_int MAX = ~MIN; |
| 30 | if (a == MIN) |
| 31 | { |
| 32 | if (b == 0 || b == 1) |
| 33 | return a * b; |
Daniel Dunbar | 48f46ac | 2010-03-31 17:00:45 +0000 | [diff] [blame] | 34 | compilerrt_abort(); |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 35 | } |
| 36 | if (b == MIN) |
| 37 | { |
| 38 | if (a == 0 || a == 1) |
| 39 | return a * b; |
Daniel Dunbar | 48f46ac | 2010-03-31 17:00:45 +0000 | [diff] [blame] | 40 | compilerrt_abort(); |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 41 | } |
| 42 | ti_int sa = a >> (N - 1); |
| 43 | ti_int abs_a = (a ^ sa) - sa; |
| 44 | ti_int sb = b >> (N - 1); |
| 45 | ti_int abs_b = (b ^ sb) - sb; |
| 46 | if (abs_a < 2 || abs_b < 2) |
| 47 | return a * b; |
| 48 | if (sa == sb) |
| 49 | { |
| 50 | if (abs_a > MAX / abs_b) |
Daniel Dunbar | 48f46ac | 2010-03-31 17:00:45 +0000 | [diff] [blame] | 51 | compilerrt_abort(); |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 52 | } |
| 53 | else |
| 54 | { |
| 55 | if (abs_a > MIN / -abs_b) |
Daniel Dunbar | 48f46ac | 2010-03-31 17:00:45 +0000 | [diff] [blame] | 56 | compilerrt_abort(); |
Daniel Dunbar | b3a6901 | 2009-06-26 16:47:03 +0000 | [diff] [blame] | 57 | } |
| 58 | return a * b; |
| 59 | } |
| 60 | |
| 61 | #endif |