cosmopolitan/libc/nexgen32e/strcmp-avx.S
Justine Tunney f4f4caab0e Add x86_64-linux-gnu emulator
I wanted a tiny scriptable meltdown proof way to run userspace programs
and visualize how program execution impacts memory. It helps to explain
how things like Actually Portable Executable works. It can show you how
the GCC generated code is going about manipulating matrices and more. I
didn't feel fully comfortable with Qemu and Bochs because I'm not smart
enough to understand them. I wanted something like gVisor but with much
stronger levels of assurances. I wanted a single binary that'll run, on
all major operating systems with an embedded GPL barrier ZIP filesystem
that is tiny enough to transpile to JavaScript and run in browsers too.

https://justine.storage.googleapis.com/emulator625.mp4
2020-08-25 04:43:42 -07:00

90 lines
3.2 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/macros.h"
/ Compares NUL-terminated strings w/ AVX (2011+)
/
/ @param rdi first string
/ @param rsi second string
/ @return 0 if equal, etc.
/ @asyncsignalsafe
strcmp$avx:
or $-1,%rdx
/ fallthrough
.endfn strcmp$avx,globl,hidden
/ Compares NUL-terminated strings, with byte limit.
/
/ @param rdi first string
/ @param rsi second string
/ @param rdx maximum number of bytes to compare
/ @return 0 if equal, etc.
/ @asyncsignalsafe
strncmp$avx:
.leafprologue
.profilable
cmp %rsi,%rdi
je 1f
mov $-16,%rcx
vpxor %xmm0,%xmm0,%xmm0
vpcmpeqd %xmm1,%xmm1,%xmm1
3: add $16,%rcx
4: lea 16(%rcx),%rax
cmp %rdx,%rax
ja 9f
lea (%rdi,%rcx),%eax
and $0xfff,%eax
cmp $0xff0,%eax
ja 9f
lea (%rsi,%rcx),%eax
and $0xfff,%eax
cmp $0xff0,%eax
jbe 7f
9: cmpq %rcx,%rdx
je 1f
movzbl (%rdi,%rcx),%r8d
movzbl (%rsi,%rcx),%r9d
mov %r8d,%eax
sub %r9d,%eax
testl %r8d,%r8d
je 5f
incq %rcx
testl %eax,%eax
je 4b
jmp 5f
1: xor %eax,%eax
5: .leafepilogue
7: vmovdqu (%rsi,%rcx),%xmm3
vpcmpeqb (%rdi,%rcx),%xmm3,%xmm2
vpcmpeqb %xmm0,%xmm3,%xmm3
vpandn %xmm1,%xmm2,%xmm2
vpor %xmm3,%xmm2,%xmm2
vpmovmskb %xmm2,%eax
bsf %eax,%eax
jz 3b
mov %eax,%edx
add %rdx,%rdi
movzbl (%rcx,%rdi),%eax
add %rdx,%rsi
movzbl (%rcx,%rsi),%ecx
sub %ecx,%eax
jmp 5b
.endfn strncmp$avx,globl,hidden
.source __FILE__