1*412f47f9SXin Li/* 2*412f47f9SXin Li * __strcmp_aarch64_sve - compare two strings 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 (__strcmp_aarch64_sve) 18*412f47f9SXin Li PTR_ARG (0) 19*412f47f9SXin Li PTR_ARG (1) 20*412f47f9SXin Li setffr /* initialize FFR */ 21*412f47f9SXin Li ptrue p1.b, all /* all ones; loop invariant */ 22*412f47f9SXin Li mov x2, 0 /* initialize offset */ 23*412f47f9SXin Li 24*412f47f9SXin Li /* Read a vector's worth of bytes, stopping on first fault. */ 25*412f47f9SXin Li .p2align 4 26*412f47f9SXin Li0: ldff1b z0.b, p1/z, [x0, x2] 27*412f47f9SXin Li ldff1b z1.b, p1/z, [x1, x2] 28*412f47f9SXin Li rdffrs p0.b, p1/z 29*412f47f9SXin Li b.nlast 2f 30*412f47f9SXin Li 31*412f47f9SXin Li /* First fault did not fail: the whole vector is valid. 32*412f47f9SXin Li Avoid depending on the contents of FFR beyond the branch. */ 33*412f47f9SXin Li incb x2, all /* skip bytes for next round */ 34*412f47f9SXin Li cmpeq p2.b, p1/z, z0.b, z1.b /* compare strings */ 35*412f47f9SXin Li cmpne p3.b, p1/z, z0.b, 0 /* search for ~zero */ 36*412f47f9SXin Li nands p2.b, p1/z, p2.b, p3.b /* ~(eq & ~zero) -> ne | zero */ 37*412f47f9SXin Li b.none 0b 38*412f47f9SXin Li 39*412f47f9SXin Li /* Found end-of-string or inequality. */ 40*412f47f9SXin Li1: brkb p2.b, p1/z, p2.b /* find first such */ 41*412f47f9SXin Li lasta w0, p2, z0.b /* extract each char */ 42*412f47f9SXin Li lasta w1, p2, z1.b 43*412f47f9SXin Li sub x0, x0, x1 /* return comparison */ 44*412f47f9SXin Li ret 45*412f47f9SXin Li 46*412f47f9SXin Li /* First fault failed: only some of the vector is valid. 47*412f47f9SXin Li Perform the comparison only on the valid bytes. */ 48*412f47f9SXin Li2: incp x2, p0.b /* skip bytes for next round */ 49*412f47f9SXin Li setffr /* re-init FFR for next round */ 50*412f47f9SXin Li cmpeq p2.b, p0/z, z0.b, z1.b /* compare strings, as above */ 51*412f47f9SXin Li cmpne p3.b, p0/z, z0.b, 0 52*412f47f9SXin Li nands p2.b, p0/z, p2.b, p3.b 53*412f47f9SXin Li b.none 0b 54*412f47f9SXin Li b 1b 55*412f47f9SXin Li 56*412f47f9SXin LiEND (__strcmp_aarch64_sve) 57*412f47f9SXin Li 58*412f47f9SXin Li#endif 59*412f47f9SXin Li 60