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51 lines
2.4 KiB
ArmAsm
51 lines
2.4 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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/ Returns length of NUL-terminated string.
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/
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/ @param rdi is non-null NUL-terminated string pointer
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/ @return rax is number of bytes (excluding NUL)
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/ @clob ax,dx,cx,xmm3,xmm4
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/ @note h/t agner fog
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/ @asyncsignalsafe
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strlen: .leafprologue
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.profilable
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mov %rdi,%rax
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mov %edi,%ecx
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and $15,%ecx
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and $-16,%rax
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pxor %xmm4,%xmm4
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movdqa (%rax),%xmm3
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pcmpeqb %xmm4,%xmm3
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pmovmskb %xmm3,%edx
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shr %cl,%edx
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shl %cl,%edx
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bsf %edx,%edx
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jnz 2f
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1: lea 16(%rax),%rax
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movdqa (%rax),%xmm3
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pcmpeqb %xmm4,%xmm3
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pmovmskb %xmm3,%edx
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bsf %edx,%edx
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jz 1b
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2: add %rdx,%rax
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sub %rdi,%rax
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.leafepilogue
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.endfn strlen,globl
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