| //===-- mulvti3.c - Implement __mulvti3 -----------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements __mulvti3 for the compiler_rt library. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "int_lib.h" |
| |
| #ifdef CRT_HAS_128BIT |
| |
| // Returns: a * b |
| |
| // Effects: aborts if a * b overflows |
| |
| COMPILER_RT_ABI ti_int __mulvti3(ti_int a, ti_int b) { |
| const int N = (int)(sizeof(ti_int) * CHAR_BIT); |
| const ti_int MIN = (ti_int)1 << (N - 1); |
| const ti_int MAX = ~MIN; |
| if (a == MIN) { |
| if (b == 0 || b == 1) |
| return a * b; |
| compilerrt_abort(); |
| } |
| if (b == MIN) { |
| if (a == 0 || a == 1) |
| return a * b; |
| compilerrt_abort(); |
| } |
| ti_int sa = a >> (N - 1); |
| ti_int abs_a = (a ^ sa) - sa; |
| ti_int sb = b >> (N - 1); |
| ti_int abs_b = (b ^ sb) - sb; |
| if (abs_a < 2 || abs_b < 2) |
| return a * b; |
| if (sa == sb) { |
| if (abs_a > MAX / abs_b) |
| compilerrt_abort(); |
| } else { |
| if (abs_a > MIN / -abs_b) |
| compilerrt_abort(); |
| } |
| return a * b; |
| } |
| |
| #endif // CRT_HAS_128BIT |