mulodi4.c (1606B)
1 /*===-- mulodi4.c - Implement __mulodi4 -----------------------------------=== 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is dual licensed under the MIT and the University of Illinois Open 6 * Source Licenses. See LICENSE.TXT for details. 7 * 8 * ===----------------------------------------------------------------------=== 9 * 10 * This file implements __mulodi4 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #if 0 16 #include "int_lib.h" 17 #else 18 #define COMPILER_RT_ABI 19 #define di_int int64_t 20 #define di_uint uint64_t 21 #include "lib/cc/torint.h" 22 23 di_int __mulodi4(di_int a, di_int b, int* overflow); 24 #endif 25 26 /* Returns: a * b */ 27 28 /* Effects: sets *overflow to 1 if a * b overflows */ 29 30 COMPILER_RT_ABI di_int 31 __mulodi4(di_int a, di_int b, int* overflow) 32 { 33 const int N = (int)(sizeof(di_int) * CHAR_BIT); 34 const di_int MIN = (di_int) ((di_uint)1 << (N-1)); 35 const di_int MAX = ~MIN; 36 *overflow = 0; 37 di_int result = a * b; 38 if (a == MIN) 39 { 40 if (b != 0 && b != 1) 41 *overflow = 1; 42 return result; 43 } 44 if (b == MIN) 45 { 46 if (a != 0 && a != 1) 47 *overflow = 1; 48 return result; 49 } 50 di_int sa = a >> (N - 1); 51 di_int abs_a = (a ^ sa) - sa; 52 di_int sb = b >> (N - 1); 53 di_int abs_b = (b ^ sb) - sb; 54 if (abs_a < 2 || abs_b < 2) 55 return result; 56 if (sa == sb) 57 { 58 if (abs_a > MAX / abs_b) 59 *overflow = 1; 60 } 61 else 62 { 63 if (abs_a > MIN / -abs_b) 64 *overflow = 1; 65 } 66 return result; 67 }