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strcpy-sve.S
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strcpy-sve.S
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/*
* strcpy/stpcpy - copy a string returning pointer to start/end.
*
* Copyright (c) 2018-2022, Arm Limited.
* SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
*/
#include "asmdefs.h"
#if __ARM_FEATURE_SVE
/* Assumptions:
*
* ARMv8-a, AArch64
* SVE Available.
*/
/* To build as stpcpy, define BUILD_STPCPY before compiling this file. */
#ifdef BUILD_STPCPY
#define FUNC __stpcpy_aarch64_sve
#else
#define FUNC __strcpy_aarch64_sve
#endif
ENTRY (FUNC)
PTR_ARG (0)
PTR_ARG (1)
setffr /* initialize FFR */
ptrue p2.b, all /* all ones; loop invariant */
mov x2, 0 /* initialize offset */
.p2align 4
/* Read a vector's worth of bytes, stopping on first fault. */
0: ldff1b z0.b, p2/z, [x1, x2]
rdffrs p0.b, p2/z
b.nlast 1f
/* First fault did not fail: the whole vector is valid.
Avoid depending on the contexts of FFR beyond the branch. */
cmpeq p1.b, p2/z, z0.b, 0 /* search for zeros */
b.any 2f
/* No zero found. Store the whole vector and loop. */
st1b z0.b, p2, [x0, x2]
incb x2, all
b 0b
/* First fault failed: only some of the vector is valid.
Perform the comparison only on the valid bytes. */
1: cmpeq p1.b, p0/z, z0.b, 0 /* search for zeros */
b.any 2f
/* No zero found. Store the valid portion of the vector and loop. */
setffr /* re-init FFR */
st1b z0.b, p0, [x0, x2]
incp x2, p0.b
b 0b
/* Zero found. Crop the vector to the found zero and finish. */
2: brka p0.b, p2/z, p1.b
st1b z0.b, p0, [x0, x2]
#ifdef BUILD_STPCPY
add x0, x0, x2
sub x0, x0, 1
incp x0, p0.b
#endif
ret
END (FUNC)
#endif