1 /* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------=== 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 __mulvti3 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #if __x86_64 16 17 #include "int_lib.h" 18 #include <stdlib.h> 19 20 /* Returns: a * b */ 21 22 /* Effects: aborts if a * b overflows */ 23 24 ti_int 25 __mulvti3(ti_int a, ti_int b) 26 { 27 const int N = (int)(sizeof(ti_int) * CHAR_BIT); 28 const ti_int MIN = (ti_int)1 << (N-1); 29 const ti_int MAX = ~MIN; 30 if (a == MIN) 31 { 32 if (b == 0 || b == 1) 33 return a * b; 34 abort(); 35 } 36 if (b == MIN) 37 { 38 if (a == 0 || a == 1) 39 return a * b; 40 abort(); 41 } 42 ti_int sa = a >> (N - 1); 43 ti_int abs_a = (a ^ sa) - sa; 44 ti_int sb = b >> (N - 1); 45 ti_int abs_b = (b ^ sb) - sb; 46 if (abs_a < 2 || abs_b < 2) 47 return a * b; 48 if (sa == sb) 49 { 50 if (abs_a > MAX / abs_b) 51 abort(); 52 } 53 else 54 { 55 if (abs_a > MIN / -abs_b) 56 abort(); 57 } 58 return a * b; 59 } 60 61 #endif 62
