cosmopolitan/libc/nexgen32e/memrchr16.S

65 lines
2.8 KiB
ArmAsm

/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program 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; version 2 of the License. │
This program 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.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software │
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "libc/nexgen32e/x86feature.h"
#include "libc/dce.h"
#include "libc/macros.h"
/ Searches for last instance of uint16_t in memory region.
/
/ @param rdi points to data to search
/ @param esi is treated as uint16_t
/ @param rdx is short count in rdi
/ @return rax is address of last %si in %rdi, or NULL
/ @note AVX2 requires Haswell (2014+) or Excavator (2015+)
memrchr16:
.leafprologue
.profilable
#if !IsTiny()
cmp $16,%rdx
jb 5f
testb X86_HAVE(AVX2)+kCpuids(%rip)
jz 5f
vmovd %esi,%xmm0
vpbroadcastw %xmm0,%ymm0
3: vmovdqu -32(%rdi,%rdx,2),%ymm1
vpcmpeqw %ymm1,%ymm0,%ymm1
vpmovmskb %ymm1,%eax
lzcnt %eax,%eax
shr %eax
mov %eax,%ecx
sub %rcx,%rdx
cmp $16,%eax
jne 5f
cmp $15,%rdx
ja 3b
vzeroupper
#endif
5: xor %eax,%eax
mov %rdx,%rcx
6: sub $1,%rcx
jb 9f
cmp %si,-2(%rdi,%rdx,2)
mov %rcx,%rdx
jne 6b
lea (%rdi,%rcx,2),%rax
9: .leafepilogue
.endfn memrchr16,globl
.source __FILE__