1*412f47f9SXin Li/* 2*412f47f9SXin Li * strncmp - compare two strings with limit 3*412f47f9SXin Li * 4*412f47f9SXin Li * Copyright (c) 2018-2022, 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 (__strncmp_aarch64_sve) 18*412f47f9SXin Li PTR_ARG (0) 19*412f47f9SXin Li PTR_ARG (1) 20*412f47f9SXin Li SIZE_ARG (2) 21*412f47f9SXin Li setffr /* initialize FFR */ 22*412f47f9SXin Li mov x3, 0 /* initialize off */ 23*412f47f9SXin Li 24*412f47f9SXin Li0: whilelo p0.b, x3, x2 /* while off < max */ 25*412f47f9SXin Li b.none 9f 26*412f47f9SXin Li 27*412f47f9SXin Li ldff1b z0.b, p0/z, [x0, x3] 28*412f47f9SXin Li ldff1b z1.b, p0/z, [x1, x3] 29*412f47f9SXin Li rdffrs p1.b, p0/z 30*412f47f9SXin Li b.nlast 2f 31*412f47f9SXin Li 32*412f47f9SXin Li /* First fault did not fail: the vector up to max is valid. 33*412f47f9SXin Li Avoid depending on the contents of FFR beyond the branch. 34*412f47f9SXin Li Increment for a whole vector, even if we've only read a partial. 35*412f47f9SXin Li This is significantly cheaper than INCP, and since OFF is not 36*412f47f9SXin Li used after the loop it is ok to increment OFF past MAX. */ 37*412f47f9SXin Li incb x3 38*412f47f9SXin Li cmpeq p1.b, p0/z, z0.b, z1.b /* compare strings */ 39*412f47f9SXin Li cmpne p2.b, p0/z, z0.b, 0 /* search for ~zero */ 40*412f47f9SXin Li nands p2.b, p0/z, p1.b, p2.b /* ~(eq & ~zero) -> ne | zero */ 41*412f47f9SXin Li b.none 0b 42*412f47f9SXin Li 43*412f47f9SXin Li /* Found end-of-string or inequality. */ 44*412f47f9SXin Li1: brkb p2.b, p0/z, p2.b /* find first such */ 45*412f47f9SXin Li lasta w0, p2, z0.b /* extract each char */ 46*412f47f9SXin Li lasta w1, p2, z1.b 47*412f47f9SXin Li sub x0, x0, x1 /* return comparison */ 48*412f47f9SXin Li ret 49*412f47f9SXin Li 50*412f47f9SXin Li /* First fault failed: only some of the vector is valid. 51*412f47f9SXin Li Perform the comparison only on the valid bytes. */ 52*412f47f9SXin Li2: cmpeq p2.b, p1/z, z0.b, z1.b /* compare strings, as above */ 53*412f47f9SXin Li cmpne p3.b, p1/z, z0.b, 0 54*412f47f9SXin Li nands p2.b, p1/z, p2.b, p3.b 55*412f47f9SXin Li b.any 1b 56*412f47f9SXin Li 57*412f47f9SXin Li /* No inequality or zero found. Re-init FFR, incr and loop. */ 58*412f47f9SXin Li setffr 59*412f47f9SXin Li incp x3, p1.b 60*412f47f9SXin Li b 0b 61*412f47f9SXin Li 62*412f47f9SXin Li /* Found end-of-count. */ 63*412f47f9SXin Li9: mov x0, 0 /* return equal */ 64*412f47f9SXin Li ret 65*412f47f9SXin Li 66*412f47f9SXin LiEND (__strncmp_aarch64_sve) 67*412f47f9SXin Li 68*412f47f9SXin Li#endif 69*412f47f9SXin Li 70