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75 lines
1.5 KiB
75 lines
1.5 KiB
/*
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* strnlen - calculate the length of a string with limit.
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*
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* Copyright (c) 2019-2021, Arm Limited.
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* SPDX-License-Identifier: MIT
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*/
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#include "../asmdefs.h"
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#if __ARM_FEATURE_SVE
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/* Assumptions:
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*
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* ARMv8-a, AArch64
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* SVE Available.
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*/
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ENTRY (__strnlen_aarch64_sve)
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PTR_ARG (0)
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SIZE_ARG (1)
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setffr /* initialize FFR */
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mov x2, 0 /* initialize len */
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b 1f
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.p2align 4
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/* We have off + vl <= max, and so may read the whole vector. */
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0: ldff1b z0.b, p0/z, [x0, x2]
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rdffrs p1.b, p0/z
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b.nlast 2f
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/* First fault did not fail: the whole vector is valid.
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Avoid depending on the contents of FFR beyond the branch. */
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cmpeq p2.b, p0/z, z0.b, 0
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b.any 8f
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incb x2
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1: whilelo p0.b, x2, x1
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b.last 0b
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/* We have off + vl < max. Test for off == max before proceeding. */
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b.none 9f
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ldff1b z0.b, p0/z, [x0, x2]
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rdffrs p1.b, p0/z
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b.nlast 2f
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/* First fault did not fail: the vector up to max is valid.
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Avoid depending on the contents of FFR beyond the branch.
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Compare for end-of-string, but there are no more bytes. */
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cmpeq p2.b, p0/z, z0.b, 0
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/* Found end-of-string or zero. */
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8: brkb p2.b, p0/z, p2.b
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mov x0, x2
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incp x0, p2.b
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ret
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/* First fault failed: only some of the vector is valid.
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Perform the comparison only on the valid bytes. */
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2: cmpeq p2.b, p1/z, z0.b, 0
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b.any 8b
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/* No inequality or zero found. Re-init FFR, incr and loop. */
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setffr
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incp x2, p1.b
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b 1b
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/* End of count. Return max. */
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9: mov x0, x1
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ret
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END (__strnlen_aarch64_sve)
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#endif
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