1 /* ===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------=== 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is distributed under the University of Illinois Open Source 6 * License. See LICENSE.TXT for details. 7 * 8 * ===----------------------------------------------------------------------=== 9 * 10 * This file implements __mulvsi3 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #include "int_lib.h" 16 #include <stdlib.h> 17 18 /* Returns: a * b */ 19 20 /* Effects: aborts if a * b overflows */ 21 22 si_int 23 __mulvsi3(si_int a, si_int b) 24 { 25 const int N = (int)(sizeof(si_int) * CHAR_BIT); 26 const si_int MIN = (si_int)1 << (N-1); 27 const si_int MAX = ~MIN; 28 if (a == MIN) 29 { 30 if (b == 0 || b == 1) 31 return a * b; 32 abort(); 33 } 34 if (b == MIN) 35 { 36 if (a == 0 || a == 1) 37 return a * b; 38 abort(); 39 } 40 si_int sa = a >> (N - 1); 41 si_int abs_a = (a ^ sa) - sa; 42 si_int sb = b >> (N - 1); 43 si_int abs_b = (b ^ sb) - sb; 44 if (abs_a < 2 || abs_b < 2) 45 return a * b; 46 if (sa == sb) 47 { 48 if (abs_a > MAX / abs_b) 49 abort(); 50 } 51 else 52 { 53 if (abs_a > MIN / -abs_b) 54 abort(); 55 } 56 return a * b; 57 } 58
