1 //===-- mulodi4.c - Implement __mulodi4 -----------------------------------===// 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 // This file implements __mulodi4 for the compiler_rt library. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "int_lib.h" 14 15 // Returns: a * b 16 17 // Effects: sets *overflow to 1 if a * b overflows 18 19 COMPILER_RT_ABI di_int __mulodi4(di_int a, di_int b, int *overflow) { 20 const int N = (int)(sizeof(di_int) * CHAR_BIT); 21 const di_int MIN = (di_int)1 << (N - 1); 22 const di_int MAX = ~MIN; 23 *overflow = 0; 24 di_int result = a * b; 25 if (a == MIN) { 26 if (b != 0 && b != 1) 27 *overflow = 1; 28 return result; 29 } 30 if (b == MIN) { 31 if (a != 0 && a != 1) 32 *overflow = 1; 33 return result; 34 } 35 di_int sa = a >> (N - 1); 36 di_int abs_a = (a ^ sa) - sa; 37 di_int sb = b >> (N - 1); 38 di_int abs_b = (b ^ sb) - sb; 39 if (abs_a < 2 || abs_b < 2) 40 return result; 41 if (sa == sb) { 42 if (abs_a > MAX / abs_b) 43 *overflow = 1; 44 } else { 45 if (abs_a > MIN / -abs_b) 46 *overflow = 1; 47 } 48 return result; 49 } 50