| 1 | //===-- int_mulv_impl.inc - Implement __mulv[sdt]i3 ---------------*- C -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // Helper used by __mulvsi3, __mulvdi3 and __mulvti3. |
| 10 | // |
| 11 | //===----------------------------------------------------------------------===// |
| 12 | |
| 13 | #include "int_lib.h" |
| 14 | |
| 15 | // Returns: a * b |
| 16 | |
| 17 | // Effects: aborts if a * b overflows |
| 18 | |
| 19 | static __inline fixint_t __mulvXi3(fixint_t a, fixint_t b) { |
| 20 | const int N = (int)(sizeof(fixint_t) * CHAR_BIT); |
| 21 | const fixint_t MIN = (fixint_t)((fixuint_t)1 << (N - 1)); |
| 22 | const fixint_t MAX = ~MIN; |
| 23 | if (a == MIN) { |
| 24 | if (b == 0 || b == 1) |
| 25 | return a * b; |
| 26 | compilerrt_abort(); |
| 27 | } |
| 28 | if (b == MIN) { |
| 29 | if (a == 0 || a == 1) |
| 30 | return a * b; |
| 31 | compilerrt_abort(); |
| 32 | } |
| 33 | fixint_t sa = a >> (N - 1); |
| 34 | fixint_t abs_a = (a ^ sa) - sa; |
| 35 | fixint_t sb = b >> (N - 1); |
| 36 | fixint_t abs_b = (b ^ sb) - sb; |
| 37 | if (abs_a < 2 || abs_b < 2) |
| 38 | return a * b; |
| 39 | if (sa == sb) { |
| 40 | if (abs_a > MAX / abs_b) |
| 41 | compilerrt_abort(); |
| 42 | } else { |
| 43 | if (abs_a > MIN / -abs_b) |
| 44 | compilerrt_abort(); |
| 45 | } |
| 46 | return a * b; |
| 47 | } |
| 48 |