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70 lines
1.8 KiB
70 lines
1.8 KiB
/*
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* strncmp - compare two strings with limit
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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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#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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.arch armv8-a+sve
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.text
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.globl __strncmp_aarch64_sve
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.type __strncmp_aarch64_sve, %function
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.p2align 4
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__strncmp_aarch64_sve:
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setffr /* initialize FFR */
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mov x3, 0 /* initialize off */
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0: whilelo p0.b, x3, x2 /* while off < max */
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b.none 9f
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ldff1b z0.b, p0/z, [x0, x3]
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ldff1b z1.b, p0/z, [x1, x3]
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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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Increment for a whole vector, even if we've only read a partial.
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This is significantly cheaper than INCP, and since OFF is not
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used after the loop it is ok to increment OFF past MAX. */
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incb x3
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cmpeq p1.b, p0/z, z0.b, z1.b /* compare strings */
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cmpne p2.b, p0/z, z0.b, 0 /* search for ~zero */
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nands p2.b, p0/z, p1.b, p2.b /* ~(eq & ~zero) -> ne | zero */
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b.none 0b
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/* Found end-of-string or inequality. */
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1: brkb p2.b, p0/z, p2.b /* find first such */
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lasta w0, p2, z0.b /* extract each char */
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lasta w1, p2, z1.b
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sub x0, x0, x1 /* return comparison */
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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, z1.b /* compare strings, as above */
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cmpne p3.b, p1/z, z0.b, 0
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nands p2.b, p1/z, p2.b, p3.b
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b.any 1b
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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 x3, p1.b
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b 0b
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/* Found end-of-count. */
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9: mov x0, 0 /* return equal */
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ret
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.size __strncmp_aarch64_sve, . - __strncmp_aarch64_sve
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#endif
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