1229109Sed/*===-- mulodi4.c - Implement __mulodi4 -----------------------------------=== 2229109Sed * 3229109Sed * The LLVM Compiler Infrastructure 4229109Sed * 5229109Sed * This file is dual licensed under the MIT and the University of Illinois Open 6229109Sed * Source Licenses. See LICENSE.TXT for details. 7229109Sed * 8229109Sed * ===----------------------------------------------------------------------=== 9229109Sed * 10229109Sed * This file implements __mulodi4 for the compiler_rt library. 11229109Sed * 12229109Sed * ===----------------------------------------------------------------------=== 13229109Sed */ 14229109Sed 15229109Sed#include "int_lib.h" 16229109Sed 17229109Sed/* Returns: a * b */ 18229109Sed 19229109Sed/* Effects: sets *overflow to 1 if a * b overflows */ 20229109Sed 21229109Seddi_int 22229109Sed__mulodi4(di_int a, di_int b, int* overflow) 23229109Sed{ 24229109Sed const int N = (int)(sizeof(di_int) * CHAR_BIT); 25229109Sed const di_int MIN = (di_int)1 << (N-1); 26229109Sed const di_int MAX = ~MIN; 27229109Sed *overflow = 0; 28229109Sed di_int result = a * b; 29229109Sed if (a == MIN) 30229109Sed { 31229109Sed if (b != 0 && b != 1) 32229109Sed *overflow = 1; 33229109Sed return result; 34229109Sed } 35229109Sed if (b == MIN) 36229109Sed { 37229109Sed if (a != 0 && a != 1) 38229109Sed *overflow = 1; 39229109Sed return result; 40229109Sed } 41229109Sed di_int sa = a >> (N - 1); 42229109Sed di_int abs_a = (a ^ sa) - sa; 43229109Sed di_int sb = b >> (N - 1); 44229109Sed di_int abs_b = (b ^ sb) - sb; 45229109Sed if (abs_a < 2 || abs_b < 2) 46229109Sed return result; 47229109Sed if (sa == sb) 48229109Sed { 49229109Sed if (abs_a > MAX / abs_b) 50229109Sed *overflow = 1; 51229109Sed } 52229109Sed else 53229109Sed { 54229109Sed if (abs_a > MIN / -abs_b) 55229109Sed *overflow = 1; 56229109Sed } 57229109Sed return result; 58229109Sed} 59