llvm-project/compiler-rt/lib/builtins/divsi3.c

/* ===-- divsi3.c - Implement __divsi3 -------------------------------------===
 *
 *                     The LLVM Compiler Infrastructure
 *
 * This file is dual licensed under the MIT and the University of Illinois Open
 * Source Licenses. See LICENSE.TXT for details.
 *
 * ===----------------------------------------------------------------------===
 *
 * This file implements __divsi3 for the compiler_rt library.
 *
 * ===----------------------------------------------------------------------===
 */

#include "int_lib.h"

/* Returns: a / b */

COMPILER_RT_ABI si_int
__divsi3(si_int a, si_int b)
{
    const int bits_in_word_m1 = (int)(sizeof(si_int) * CHAR_BIT) - 1;
    si_int s_a = a >> bits_in_word_m1;           /* s_a = a < 0 ? -1 : 0 */
    si_int s_b = b >> bits_in_word_m1;           /* s_b = b < 0 ? -1 : 0 */
    a = (a ^ s_a) - s_a;                         /* negate if s_a == -1 */
    b = (b ^ s_b) - s_b;                         /* negate if s_b == -1 */
    s_a ^= s_b;                                  /* sign of quotient */
    /*
     * On CPUs without unsigned hardware division support,
     *  this calls __udivsi3 (notice the cast to su_int).
     * On CPUs with unsigned hardware division support,
     *  this uses the unsigned division instruction.
     */
    return ((su_int)a/(su_int)b ^ s_a) - s_a;    /* negate if s_a == -1 */
}

#if defined(__ARM_EABI__)
AEABI_RTABI si_int __aeabi_idiv(si_int a, si_int b) COMPILER_RT_ALIAS(__divsi3);
#endif