68 lines
2.9 KiB
ArmAsm
68 lines
2.9 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 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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│ 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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#include "libc/macros.h"
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/ Fast log₁₀ when 𝑥 is an integer.
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/
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/ @param rdi is uint64 𝑥
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/ @domain 0<𝑥<2⁶⁴ ∧ 𝑥∊ℤ
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llog10: .leafprologue
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.profilable
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bsr %rdi,%rax
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jz 3f
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lea llog10data(%rip),%rdx
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movsbl 1(%rdx,%rax),%eax
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cmp 2f-1f(%rdx,%rax,8),%rdi
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sbb $0,%al
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jmp 4f
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3: xor %eax,%eax # domain error
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4: .leafepilogue
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.endfn llog10,globl
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.rodata
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llog10data:
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1: .byte 0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4
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.byte 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9
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.byte 9, 9,10,10,10,11,11,11,12,12,12,12,13,13,13,14
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.byte 14,14,15,15,15,15,16,16,16,17,17,17,18,18,18,18
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.byte 19,19,19
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.align 8
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2: .quad 0
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.quad 10
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.quad 100
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.quad 1000
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.quad 10000
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.quad 100000
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.quad 1000000
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.quad 10000000
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.quad 100000000
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.quad 1000000000
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.quad 10000000000
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.quad 100000000000
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.quad 1000000000000
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.quad 10000000000000
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.quad 100000000000000
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.quad 1000000000000000
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.quad 10000000000000000
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.quad 100000000000000000
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.endobj llog10data
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.previous
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.source __FILE__
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