2020-06-16 13:38:43 +00:00
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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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2020-06-15 14:18:57 +00:00
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│vi: set et ft=asm ts=8 sw=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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2020-12-28 01:18:44 +00:00
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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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2020-06-15 14:18:57 +00:00
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│ │
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2020-12-28 01:18:44 +00:00
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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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2020-06-15 14:18:57 +00:00
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╚─────────────────────────────────────────────────────────────────────────────*/
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/* clang-format off */
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2021-02-08 17:19:00 +00:00
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// Searches for substring.
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//
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// @param rdi is NUL-terminated haystack string
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// @param rsi is NUL-terminated needle string (16-byte aligned)
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// @return rax is pointer to substring or NULL
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// @todo 10x faster than naïve but could be 100x faster
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2020-06-15 14:18:57 +00:00
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.macro .strstr mode:req
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push %rbp
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mov %rsp,%rbp
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.profilable
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sub $32,%rsp
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mov %rdi,%rax
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xor %ecx,%ecx
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0: mov $-16,%rdx
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1: add $16,%rdx
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movaps (%rsi,%rdx),%xmm0
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2: add %rcx,%rax
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lea (%rax,%rdx),%rdi
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test $15,%edi
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jnz 6f
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pcmpistri $\mode,(%rdi),%xmm0
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3: ja 2b # !CF (no match) && !ZF (need NUL-term)
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jnc 4f # !CF (no match) && ZF (NUL-terminator)
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jno 0b # !OF ← CF && CX!=0 (matched at offset)
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jns 1b # !SF ← NUL ∉ XMM1 (need to match more)
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jmp 5f # youtu.be/nVk1DjMtLWs
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4: xor %eax,%eax
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5: leave
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ret
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6: mov %rdi,%r9 # same w/ pointer realign
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and $15,%r9d
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mov %edi,%r8d
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and $0xfff,%r8d
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cmp $0xff0,%r8d
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ja 8f
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7: pcmpistri $\mode,(%rdi),%xmm0
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cmova %r9d,%ecx
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jmp 3b
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8: pcmpeqd %xmm2,%xmm2 # handle danger memory
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mov %rdi,%r8
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and $-16,%r8
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movaps (%r8),%xmm1
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movaps %xmm1,-32(%rbp)
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movaps %xmm2,-16(%rbp)
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pcmpistri $\mode,-32(%rbp,%r9),%xmm2
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jz 4b
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jmp 7b
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.endm
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