1*412f47f9SXin Li/* 2*412f47f9SXin Li * strnlen - calculate the length of a string with limit. 3*412f47f9SXin Li * 4*412f47f9SXin Li * Copyright (c) 2019-2022, Arm Limited. 5*412f47f9SXin Li * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception 6*412f47f9SXin Li */ 7*412f47f9SXin Li 8*412f47f9SXin Li#include "asmdefs.h" 9*412f47f9SXin Li 10*412f47f9SXin Li#if __ARM_FEATURE_SVE 11*412f47f9SXin Li/* Assumptions: 12*412f47f9SXin Li * 13*412f47f9SXin Li * ARMv8-a, AArch64 14*412f47f9SXin Li * SVE Available. 15*412f47f9SXin Li */ 16*412f47f9SXin Li 17*412f47f9SXin LiENTRY (__strnlen_aarch64_sve) 18*412f47f9SXin Li PTR_ARG (0) 19*412f47f9SXin Li SIZE_ARG (1) 20*412f47f9SXin Li setffr /* initialize FFR */ 21*412f47f9SXin Li mov x2, 0 /* initialize len */ 22*412f47f9SXin Li b 1f 23*412f47f9SXin Li 24*412f47f9SXin Li .p2align 4 25*412f47f9SXin Li /* We have off + vl <= max, and so may read the whole vector. */ 26*412f47f9SXin Li0: ldff1b z0.b, p0/z, [x0, x2] 27*412f47f9SXin Li rdffrs p1.b, p0/z 28*412f47f9SXin Li b.nlast 2f 29*412f47f9SXin Li 30*412f47f9SXin Li /* First fault did not fail: the whole vector is valid. 31*412f47f9SXin Li Avoid depending on the contents of FFR beyond the branch. */ 32*412f47f9SXin Li cmpeq p2.b, p0/z, z0.b, 0 33*412f47f9SXin Li b.any 8f 34*412f47f9SXin Li incb x2 35*412f47f9SXin Li 36*412f47f9SXin Li1: whilelo p0.b, x2, x1 37*412f47f9SXin Li b.last 0b 38*412f47f9SXin Li 39*412f47f9SXin Li /* We have off + vl < max. Test for off == max before proceeding. */ 40*412f47f9SXin Li b.none 9f 41*412f47f9SXin Li 42*412f47f9SXin Li ldff1b z0.b, p0/z, [x0, x2] 43*412f47f9SXin Li rdffrs p1.b, p0/z 44*412f47f9SXin Li b.nlast 2f 45*412f47f9SXin Li 46*412f47f9SXin Li /* First fault did not fail: the vector up to max is valid. 47*412f47f9SXin Li Avoid depending on the contents of FFR beyond the branch. 48*412f47f9SXin Li Compare for end-of-string, but there are no more bytes. */ 49*412f47f9SXin Li cmpeq p2.b, p0/z, z0.b, 0 50*412f47f9SXin Li 51*412f47f9SXin Li /* Found end-of-string or zero. */ 52*412f47f9SXin Li8: brkb p2.b, p0/z, p2.b 53*412f47f9SXin Li mov x0, x2 54*412f47f9SXin Li incp x0, p2.b 55*412f47f9SXin Li ret 56*412f47f9SXin Li 57*412f47f9SXin Li /* First fault failed: only some of the vector is valid. 58*412f47f9SXin Li Perform the comparison only on the valid bytes. */ 59*412f47f9SXin Li2: cmpeq p2.b, p1/z, z0.b, 0 60*412f47f9SXin Li b.any 8b 61*412f47f9SXin Li 62*412f47f9SXin Li /* No inequality or zero found. Re-init FFR, incr and loop. */ 63*412f47f9SXin Li setffr 64*412f47f9SXin Li incp x2, p1.b 65*412f47f9SXin Li b 1b 66*412f47f9SXin Li 67*412f47f9SXin Li /* End of count. Return max. */ 68*412f47f9SXin Li9: mov x0, x1 69*412f47f9SXin Li ret 70*412f47f9SXin Li 71*412f47f9SXin LiEND (__strnlen_aarch64_sve) 72*412f47f9SXin Li 73*412f47f9SXin Li#endif 74*412f47f9SXin Li 75