72 lines
2.8 KiB
ArmAsm
72 lines
2.8 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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│ 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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.source __FILE__
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/ Encodes Thompson-Pike varint.
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/
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/ @param edi is int to encode
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/ @return rax is word-encoded byte buffer
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/ @clob edi,rax,flags
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/ @note invented on a napkin in a new jersey diner
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tpenc: .leafprologue
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.profilable
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push %rcx
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push %rdx
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mov %edi,%edi
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xor %eax,%eax
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cmp $127,%edi
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jbe 3f
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bsr %edi,%ecx
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ezlea kTpenc,dx
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mov -7*(1+1)(%rdx,%rcx,2),%ecx
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1: mov %edi,%edx
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shr $6,%edi
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and $0b00111111,%dl
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or $0b10000000,%al
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or %dl,%al
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shl $8,%rax
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dec %cl
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jnz 1b
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2: or %ch,%al
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3: or %rdi,%rax
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pop %rdx
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pop %rcx
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.leafepilogue
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.endfn tpenc,globl
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.rodata
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kTpenc: .rept 4 # MSB≤10 (0x7FF)
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.byte 1,0b11000000 # len,mark
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.endr
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.rept 5 # MSB≤15 (0xFFFF)
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.byte 2,0b11100000 # len,mark
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.endr
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.rept 5 # MSB≤20 (0x1FFFFF)
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.byte 3,0b11110000 # len,mark
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.endr
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.rept 5 # MSB≤25 (0x3FFFFFF)
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.byte 4,0b11111000 # len,mark
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.endr
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.rept 6 # MSB≤31 (0xffffffff)
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.byte 5,0b11111100 # len,mark
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.endr
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.endobj kTpenc
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