1 //===-- mulvti3.c - Implement __mulvti3 -----------------------------------===// 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 __mulvti3 for the compiler_rt library. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "int_lib.h" 14 15 #ifdef CRT_HAS_128BIT 16 17 // Returns: a * b 18 19 // Effects: aborts if a * b overflows 20 21 COMPILER_RT_ABI ti_int __mulvti3(ti_int a, ti_int b) { 22 const int N = (int)(sizeof(ti_int) * CHAR_BIT); 23 const ti_int MIN = (ti_int)1 << (N - 1); 24 const ti_int MAX = ~MIN; 25 if (a == MIN) { 26 if (b == 0 || b == 1) 27 return a * b; 28 compilerrt_abort(); 29 } 30 if (b == MIN) { 31 if (a == 0 || a == 1) 32 return a * b; 33 compilerrt_abort(); 34 } 35 ti_int sa = a >> (N - 1); 36 ti_int abs_a = (a ^ sa) - sa; 37 ti_int sb = b >> (N - 1); 38 ti_int abs_b = (b ^ sb) - sb; 39 if (abs_a < 2 || abs_b < 2) 40 return a * b; 41 if (sa == sb) { 42 if (abs_a > MAX / abs_b) 43 compilerrt_abort(); 44 } else { 45 if (abs_a > MIN / -abs_b) 46 compilerrt_abort(); 47 } 48 return a * b; 49 } 50 51 #endif // CRT_HAS_128BIT 52