//===-- mulodi4.c - Implement __mulodi4 -----------------------------------===// // // 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 __mulodi4 for the compiler_rt library. // //===----------------------------------------------------------------------===// #include "int_lib.h" // Returns: a * b // Effects: sets *overflow to 1 if a * b overflows COMPILER_RT_ABI di_int __mulodi4(di_int a, di_int b, int *overflow) { const int N = (int)(sizeof(di_int) * CHAR_BIT); const di_int MIN = (di_int)1 << (N - 1); const di_int MAX = ~MIN; *overflow = 0; di_int result = 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; } di_int sa = a >> (N - 1); di_int abs_a = (a ^ sa) - sa; di_int sb = b >> (N - 1); di_int 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; } |