mirror of
https://github.com/jart/cosmopolitan.git
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67 lines
2.7 KiB
ArmAsm
67 lines
2.7 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.internal.h"
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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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// @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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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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mov kTpenc-7*(1+1)(,%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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.leafepilogue
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.endfn tpenc,globl
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.rodata
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.align 4
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.underrun
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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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.zero 2
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.endobj kTpenc
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.overrun
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