1 //===-- multi3.c - Implement __multi3 -------------------------------------===// 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 __multi3 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 static ti_int __mulddi3(du_int a, du_int b) { 20 twords r; 21 const int bits_in_dword_2 = (int)(sizeof(di_int) * CHAR_BIT) / 2; 22 const du_int lower_mask = (du_int)~0 >> bits_in_dword_2; 23 r.s.low = (a & lower_mask) * (b & lower_mask); 24 du_int t = r.s.low >> bits_in_dword_2; 25 r.s.low &= lower_mask; 26 t += (a >> bits_in_dword_2) * (b & lower_mask); 27 r.s.low += (t & lower_mask) << bits_in_dword_2; 28 r.s.high = t >> bits_in_dword_2; 29 t = r.s.low >> bits_in_dword_2; 30 r.s.low &= lower_mask; 31 t += (b >> bits_in_dword_2) * (a & lower_mask); 32 r.s.low += (t & lower_mask) << bits_in_dword_2; 33 r.s.high += t >> bits_in_dword_2; 34 r.s.high += (a >> bits_in_dword_2) * (b >> bits_in_dword_2); 35 return r.all; 36 } 37 38 // Returns: a * b 39 40 COMPILER_RT_ABI ti_int __multi3(ti_int a, ti_int b) { 41 twords x; 42 x.all = a; 43 twords y; 44 y.all = b; 45 twords r; 46 r.all = __mulddi3(x.s.low, y.s.low); 47 r.s.high += x.s.high * y.s.low + x.s.low * y.s.high; 48 return r.all; 49 } 50 51 #endif // CRT_HAS_128BIT 52