gcc/libgcc/config/riscv/muldi3.S

/* Integer multiplication routines for RISC-V.

   Copyright (C) 2016-2018 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include "riscv-asm.h"

  .text
  .align 2

#if __riscv_xlen == 32
/* Our RV64 64-bit routine is equivalent to our RV32 32-bit routine.  */
# define __muldi3 __mulsi3
#endif

FUNC_BEGIN (__muldi3)
  mv     a2, a0
  li     a0, 0
.L1:
  andi   a3, a1, 1
  beqz   a3, .L2
  add    a0, a0, a2
.L2:
  srli   a1, a1, 1
  slli   a2, a2, 1
  bnez   a1, .L1
  ret
FUNC_END (__muldi3)