mirror of
https://github.com/jart/cosmopolitan.git
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2fc507c98f
* modelines: tw -> sw shiftwidth, not textwidth. * space-surround modelines * fix irregular modelines * Fix modeline in titlegen.c
139 lines
4.8 KiB
ArmAsm
139 lines
4.8 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│ vi: set noet ft=asm ts=8 sw=8 fenc=utf-8 :vi │
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╚──────────────────────────────────────────────────────────────────────────────╝
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│ │
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│ Optimized Routines │
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│ Copyright (c) 1999-2022, Arm Limited. │
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│ │
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│ Permission is hereby granted, free of charge, to any person obtaining │
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│ a copy of this software and associated documentation files (the │
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│ "Software"), to deal in the Software without restriction, including │
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│ without limitation the rights to use, copy, modify, merge, publish, │
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│ distribute, sublicense, and/or sell copies of the Software, and to │
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│ permit persons to whom the Software is furnished to do so, subject to │
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│ the following conditions: │
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│ │
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│ The above copyright notice and this permission notice shall be │
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│ included in all copies or substantial portions of the Software. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
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│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
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│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
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│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
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│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
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│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
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│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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│ │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/aarch64/asmdefs.internal.h"
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#define __memrchr_aarch64 memrchr
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.ident "\n\n\
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Optimized Routines (MIT License)\n\
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Copyright 2022 ARM Limited\n"
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.include "libc/disclaimer.inc"
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/* Assumptions:
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*
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* ARMv8-a, AArch64, Advanced SIMD.
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* MTE compatible.
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*/
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#define srcin x0
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#define chrin w1
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#define cntin x2
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#define result x0
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#define src x3
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#define cntrem x4
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#define synd x5
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#define shift x6
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#define tmp x7
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#define end x8
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#define endm1 x9
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#define vrepchr v0
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#define qdata q1
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#define vdata v1
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#define vhas_chr v2
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#define vend v3
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#define dend d3
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/*
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Core algorithm:
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For each 16-byte chunk we calculate a 64-bit nibble mask value with four bits
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per byte. We take 4 bits of every comparison byte with shift right and narrow
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by 4 instruction. Since the bits in the nibble mask reflect the order in
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which things occur in the original string, counting leading zeros identifies
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exactly which byte matched. */
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ENTRY (__memrchr_aarch64)
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PTR_ARG (0)
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add end, srcin, cntin
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sub endm1, end, 1
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bic src, endm1, 15
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cbz cntin, L(nomatch)
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ld1 {vdata.16b}, [src]
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dup vrepchr.16b, chrin
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cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
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neg shift, end, lsl 2
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shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
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fmov synd, dend
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lsl synd, synd, shift
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cbz synd, L(start_loop)
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clz synd, synd
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sub result, endm1, synd, lsr 2
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cmp cntin, synd, lsr 2
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csel result, result, xzr, hi
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ret
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nop
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L(start_loop):
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subs cntrem, src, srcin
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b.ls L(nomatch)
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/* Make sure that it won't overread by a 16-byte chunk */
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sub cntrem, cntrem, 1
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tbz cntrem, 4, L(loop32_2)
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add src, src, 16
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.p2align 5
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L(loop32):
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ldr qdata, [src, -32]!
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cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
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umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
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fmov synd, dend
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cbnz synd, L(end)
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L(loop32_2):
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ldr qdata, [src, -16]
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subs cntrem, cntrem, 32
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cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
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b.lo L(end_2)
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umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
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fmov synd, dend
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cbz synd, L(loop32)
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L(end_2):
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sub src, src, 16
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L(end):
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shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
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fmov synd, dend
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add tmp, src, 15
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#ifdef __AARCH64EB__
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rbit synd, synd
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#endif
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clz synd, synd
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sub tmp, tmp, synd, lsr 2
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cmp tmp, srcin
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csel result, tmp, xzr, hs
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ret
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L(nomatch):
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mov result, 0
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ret
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END (__memrchr_aarch64)
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