2020-12-24 07:42:56 +00:00
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/*-*- 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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2020-06-15 14:18:57 +00:00
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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2020-12-24 07:42:56 +00:00
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#include "libc/macros.h"
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2020-06-15 14:18:57 +00:00
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2020-12-24 07:42:56 +00:00
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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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