1 /* ===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------=== 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 __mulvsi3 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #include "int_lib.h" 16 17 /* Returns: a * b */ 18 19 /* Effects: aborts if a * b overflows */ 20 21 COMPILER_RT_ABI si_int 22 __mulvsi3(si_int a, si_int b) 23 { 24 const int N = (int)(sizeof(si_int) * CHAR_BIT); 25 const si_int MIN = (si_int)1 << (N-1); 26 const si_int MAX = ~MIN; 27 if (a == MIN) 28 { 29 if (b == 0 || b == 1) 30 return a * b; 31 compilerrt_abort(); 32 } 33 if (b == MIN) 34 { 35 if (a == 0 || a == 1) 36 return a * b; 37 compilerrt_abort(); 38 } 39 si_int sa = a >> (N - 1); 40 si_int abs_a = (a ^ sa) - sa; 41 si_int sb = b >> (N - 1); 42 si_int abs_b = (b ^ sb) - sb; 43 if (abs_a < 2 || abs_b < 2) 44 return a * b; 45 if (sa == sb) 46 { 47 if (abs_a > MAX / abs_b) 48 compilerrt_abort(); 49 } 50 else 51 { 52 if (abs_a > MIN / -abs_b) 53 compilerrt_abort(); 54 } 55 return a * b; 56 } 57
