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/*
* __strcmp_aarch64_sve - compare two strings
*
* Copyright (c) 2018-2021, Arm Limited.
* SPDX-License-Identifier: MIT
*/
#include "../asmdefs.h"
#if __ARM_FEATURE_SVE
/* Assumptions:
*
* ARMv8-a, AArch64
* SVE Available.
*/
ENTRY (__strcmp_aarch64_sve)
PTR_ARG (0)
PTR_ARG (1)
setffr /* initialize FFR */
ptrue p1.b, all /* all ones; loop invariant */
mov x2, 0 /* initialize offset */
/* Read a vector's worth of bytes, stopping on first fault. */
.p2align 4
0: ldff1b z0.b, p1/z, [x0, x2]
ldff1b z1.b, p1/z, [x1, x2]
rdffrs p0.b, p1/z
b.nlast 2f
/* First fault did not fail: the whole vector is valid.
Avoid depending on the contents of FFR beyond the branch. */
incb x2, all /* skip bytes for next round */
cmpeq p2.b, p1/z, z0.b, z1.b /* compare strings */
cmpne p3.b, p1/z, z0.b, 0 /* search for ~zero */
nands p2.b, p1/z, p2.b, p3.b /* ~(eq & ~zero) -> ne | zero */
b.none 0b
/* Found end-of-string or inequality. */
1: brkb p2.b, p1/z, p2.b /* find first such */
lasta w0, p2, z0.b /* extract each char */
lasta w1, p2, z1.b
sub x0, x0, x1 /* return comparison */
ret
/* First fault failed: only some of the vector is valid.
Perform the comparison only on the valid bytes. */
2: incp x2, p0.b /* skip bytes for next round */
setffr /* re-init FFR for next round */
cmpeq p2.b, p0/z, z0.b, z1.b /* compare strings, as above */
cmpne p3.b, p0/z, z0.b, 0
nands p2.b, p0/z, p2.b, p3.b
b.none 0b
b 1b
END (__strcmp_aarch64_sve)
#endif
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