compiler-rt/lib/builtins/muldi3.c

   1 //===-- muldi3.c - Implement __muldi3 -------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements __muldi3 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 // Returns: a * b
  16
  17 static di_int __muldsi3(su_int a, su_int b) {
  18   dwords r;
  19   const int bits_in_word_2 = (int)(sizeof(si_int) * CHAR_BIT) / 2;
  20   const su_int lower_mask = (su_int)~0 >> bits_in_word_2;
  21   r.s.low = (a & lower_mask) * (b & lower_mask);
  22   su_int t = r.s.low >> bits_in_word_2;
  23   r.s.low &= lower_mask;
  24   t += (a >> bits_in_word_2) * (b & lower_mask);
  25   r.s.low += (t & lower_mask) << bits_in_word_2;
  26   r.s.high = t >> bits_in_word_2;
  27   t = r.s.low >> bits_in_word_2;
  28   r.s.low &= lower_mask;
  29   t += (b >> bits_in_word_2) * (a & lower_mask);
  30   r.s.low += (t & lower_mask) << bits_in_word_2;
  31   r.s.high += t >> bits_in_word_2;
  32   r.s.high += (a >> bits_in_word_2) * (b >> bits_in_word_2);
  33   return r.all;
  34 }
  35
  36 // Returns: a * b
  37
  38 COMPILER_RT_ABI di_int __muldi3(di_int a, di_int b) {
  39   dwords x;
  40   x.all = a;
  41   dwords y;
  42   y.all = b;
  43   dwords r;
  44   r.all = __muldsi3(x.s.low, y.s.low);
  45   r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
  46   return r.all;
  47 }
  48
  49 #if defined(__ARM_EABI__)
  50 COMPILER_RT_ALIAS(__muldi3, __aeabi_lmul)
  51 #endif