| //===-- int_mulo_impl.inc - Implement __mulo[sdt]i4 ---------------*- C -*-===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Helper used by __mulosi4, __mulodi4 and __muloti4. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "int_lib.h" |
| |
| // Returns: a * b |
| |
| // Effects: sets *overflow to 1 if a * b overflows |
| |
| static __inline fixint_t __muloXi4(fixint_t a, fixint_t b, int *overflow) { |
| const int N = (int)(sizeof(fixint_t) * CHAR_BIT); |
| const fixint_t MIN = (fixint_t)((fixuint_t)1 << (N - 1)); |
| const fixint_t MAX = ~MIN; |
| *overflow = 0; |
| fixint_t result = (fixuint_t)a * b; |
| if (a == MIN) { |
| if (b != 0 && b != 1) |
| *overflow = 1; |
| return result; |
| } |
| if (b == MIN) { |
| if (a != 0 && a != 1) |
| *overflow = 1; |
| return result; |
| } |
| fixint_t sa = a >> (N - 1); |
| fixint_t abs_a = (a ^ sa) - sa; |
| fixint_t sb = b >> (N - 1); |
| fixint_t abs_b = (b ^ sb) - sb; |
| if (abs_a < 2 || abs_b < 2) |
| return result; |
| if (sa == sb) { |
| if (abs_a > MAX / abs_b) |
| *overflow = 1; |
| } else { |
| if (abs_a > MIN / -abs_b) |
| *overflow = 1; |
| } |
| return result; |
| } |