cosmopolitan/third_party/compiler_rt/udivsi3.c
Justine Tunney 7e0a09feec
Mint APE Loader v1.5
This change ports APE Loader to Linux AARCH64, so that Raspberry Pi
users can run programs like redbean, without the executable needing
to modify itself. Progress has also slipped into this change on the
issue of making progress better conforming to user expectations and
industry standards regarding which symbols we're allowed to declare
2023-07-26 13:54:49 -07:00

71 lines
1.9 KiB
C

/* clang-format off */
/* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------===
*
* 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 __udivsi3 for the compiler_rt library.
*
* ===----------------------------------------------------------------------===
*/
__static_yoink("huge_compiler_rt_license");
#include "third_party/compiler_rt/int_lib.h"
/* Returns: a / b */
/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
/* This function should not call __divsi3! */
COMPILER_RT_ABI su_int
__udivsi3(su_int n, su_int d)
{
const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
su_int q;
su_int r;
unsigned sr;
/* special cases */
if (d == 0)
return 0; /* ?! */
if (n == 0)
return 0;
sr = __builtin_clz(d) - __builtin_clz(n);
/* 0 <= sr <= n_uword_bits - 1 or sr large */
if (sr > n_uword_bits - 1) /* d > r */
return 0;
if (sr == n_uword_bits - 1) /* d == 1 */
return n;
++sr;
/* 1 <= sr <= n_uword_bits - 1 */
/* Not a special case */
q = n << (n_uword_bits - sr);
r = n >> sr;
su_int carry = 0;
for (; sr > 0; --sr)
{
/* r:q = ((r:q) << 1) | carry */
r = (r << 1) | (q >> (n_uword_bits - 1));
q = (q << 1) | carry;
/* carry = 0;
* if (r.all >= d.all)
* {
* r.all -= d.all;
* carry = 1;
* }
*/
const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
carry = s & 1;
r -= d & s;
}
q = (q << 1) | carry;
return q;
}
#if defined(__ARM_EABI__)
AEABI_RTABI su_int __aeabi_uidiv(su_int n, su_int d) COMPILER_RT_ALIAS(__udivsi3);
#endif