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      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 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