lib/builtins/muldi3.c

   1 /* ===-- muldi3.c - Implement __muldi3 -------------------------------------===
   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 __muldi3 for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 /* Returns: a * b */
  18
  19 static
  20 di_int
  21 __muldsi3(su_int a, su_int b)
  22 {
  23     dwords r;
  24     const int bits_in_word_2 = (int)(sizeof(si_int) * CHAR_BIT) / 2;
  25     const su_int lower_mask = (su_int)~0 >> bits_in_word_2;
  26     r.s.low = (a & lower_mask) * (b & lower_mask);
  27     su_int t = r.s.low >> bits_in_word_2;
  28     r.s.low &= lower_mask;
  29     t += (a >> bits_in_word_2) * (b & lower_mask);
  30     r.s.low += (t & lower_mask) << bits_in_word_2;
  31     r.s.high = t >> bits_in_word_2;
  32     t = r.s.low >> bits_in_word_2;
  33     r.s.low &= lower_mask;
  34     t += (b >> bits_in_word_2) * (a & lower_mask);
  35     r.s.low += (t & lower_mask) << bits_in_word_2;
  36     r.s.high += t >> bits_in_word_2;
  37     r.s.high += (a >> bits_in_word_2) * (b >> bits_in_word_2);
  38     return r.all;
  39 }
  40
  41 /* Returns: a * b */
  42
  43 ARM_EABI_FNALIAS(lmul, muldi3)
  44
  45 COMPILER_RT_ABI di_int
  46 __muldi3(di_int a, di_int b)
  47 {
  48     dwords x;
  49     x.all = a;
  50     dwords y;
  51     y.all = b;
  52     dwords r;
  53     r.all = __muldsi3(x.s.low, y.s.low);
  54     r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
  55     return r.all;
  56 }