0928368f62
This adds the Arm Optimized Routines (see https://github.com/ARM-software/optimized-routines) source code under the the LLVM license. The version of the code provided in this patch is v20.02 of the Arm Optimized Routines project. This entire contribution is being committed as is even though it does not currently fit the LLVM libc model and does not follow the LLVM coding style. In the near future, implementations from this patch will be moved over to their right place in the LLVM-libc tree. This will be done over many small patches, all of which will go through the normal LLVM code review process. See this libc-dev post for the plan: http://lists.llvm.org/pipermail/libc-dev/2020-March/000044.html Differential revision of the original upload: https://reviews.llvm.org/D75355
118 lines
3.5 KiB
ArmAsm
118 lines
3.5 KiB
ArmAsm
/*
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* strchrnul - find a character or nul in a string
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*
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* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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* See https://llvm.org/LICENSE.txt for license information.
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* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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*/
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/* Assumptions:
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*
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* ARMv8-a, AArch64
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* Neon Available.
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*/
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#include "../asmdefs.h"
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/* Arguments and results. */
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#define srcin x0
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#define chrin w1
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#define result x0
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#define src x2
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#define tmp1 x3
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#define wtmp2 w4
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#define tmp3 x5
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#define vrepchr v0
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#define vdata1 v1
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#define vdata2 v2
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#define vhas_nul1 v3
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#define vhas_nul2 v4
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#define vhas_chr1 v5
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#define vhas_chr2 v6
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#define vrepmask v7
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#define vend1 v16
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/* Core algorithm.
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For each 32-byte hunk we calculate a 64-bit syndrome value, with
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two bits per byte (LSB is always in bits 0 and 1, for both big
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and little-endian systems). For each tuple, bit 0 is set iff
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the relevant byte matched the requested character or nul. Since the
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bits in the syndrome reflect exactly the order in which things occur
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in the original string a count_trailing_zeros() operation will
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identify exactly which byte is causing the termination. */
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/* Locals and temporaries. */
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ENTRY (__strchrnul_aarch64)
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/* Magic constant 0x40100401 to allow us to identify which lane
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matches the termination condition. */
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mov wtmp2, #0x0401
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movk wtmp2, #0x4010, lsl #16
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dup vrepchr.16b, chrin
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bic src, srcin, #31 /* Work with aligned 32-byte hunks. */
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dup vrepmask.4s, wtmp2
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ands tmp1, srcin, #31
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b.eq L(loop)
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/* Input string is not 32-byte aligned. Rather than forcing
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the padding bytes to a safe value, we calculate the syndrome
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for all the bytes, but then mask off those bits of the
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syndrome that are related to the padding. */
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ld1 {vdata1.16b, vdata2.16b}, [src], #32
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neg tmp1, tmp1
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cmeq vhas_nul1.16b, vdata1.16b, #0
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cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
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cmeq vhas_nul2.16b, vdata2.16b, #0
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cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
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orr vhas_chr1.16b, vhas_chr1.16b, vhas_nul1.16b
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orr vhas_chr2.16b, vhas_chr2.16b, vhas_nul2.16b
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and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
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and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
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lsl tmp1, tmp1, #1
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addp vend1.16b, vhas_chr1.16b, vhas_chr2.16b // 256->128
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mov tmp3, #~0
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addp vend1.16b, vend1.16b, vend1.16b // 128->64
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lsr tmp1, tmp3, tmp1
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mov tmp3, vend1.d[0]
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bic tmp1, tmp3, tmp1 // Mask padding bits.
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cbnz tmp1, L(tail)
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L(loop):
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ld1 {vdata1.16b, vdata2.16b}, [src], #32
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cmeq vhas_nul1.16b, vdata1.16b, #0
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cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
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cmeq vhas_nul2.16b, vdata2.16b, #0
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cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
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/* Use a fast check for the termination condition. */
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orr vhas_chr1.16b, vhas_nul1.16b, vhas_chr1.16b
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orr vhas_chr2.16b, vhas_nul2.16b, vhas_chr2.16b
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orr vend1.16b, vhas_chr1.16b, vhas_chr2.16b
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addp vend1.2d, vend1.2d, vend1.2d
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mov tmp1, vend1.d[0]
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cbz tmp1, L(loop)
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/* Termination condition found. Now need to establish exactly why
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we terminated. */
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and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
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and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
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addp vend1.16b, vhas_chr1.16b, vhas_chr2.16b // 256->128
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addp vend1.16b, vend1.16b, vend1.16b // 128->64
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mov tmp1, vend1.d[0]
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L(tail):
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/* Count the trailing zeros, by bit reversing... */
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rbit tmp1, tmp1
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/* Re-bias source. */
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sub src, src, #32
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clz tmp1, tmp1 /* ... and counting the leading zeros. */
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/* tmp1 is twice the offset into the fragment. */
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add result, src, tmp1, lsr #1
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ret
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END (__strchrnul_aarch64)
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