1/* 2 * strncmp - compare two strings with limit 3 * 4 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 * See https://llvm.org/LICENSE.txt for license information. 6 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 */ 8 9#if __ARM_FEATURE_SVE 10/* Assumptions: 11 * 12 * ARMv8-a, AArch64 13 * SVE Available. 14 */ 15 16 .arch armv8-a+sve 17 .text 18 19 .globl __strncmp_aarch64_sve 20 .type __strncmp_aarch64_sve, %function 21 .p2align 4 22__strncmp_aarch64_sve: 23 setffr /* initialize FFR */ 24 mov x3, 0 /* initialize off */ 25 260: whilelo p0.b, x3, x2 /* while off < max */ 27 b.none 9f 28 29 ldff1b z0.b, p0/z, [x0, x3] 30 ldff1b z1.b, p0/z, [x1, x3] 31 rdffrs p1.b, p0/z 32 b.nlast 2f 33 34 /* First fault did not fail: the vector up to max is valid. 35 Avoid depending on the contents of FFR beyond the branch. 36 Increment for a whole vector, even if we've only read a partial. 37 This is significantly cheaper than INCP, and since OFF is not 38 used after the loop it is ok to increment OFF past MAX. */ 39 incb x3 40 cmpeq p1.b, p0/z, z0.b, z1.b /* compare strings */ 41 cmpne p2.b, p0/z, z0.b, 0 /* search for ~zero */ 42 nands p2.b, p0/z, p1.b, p2.b /* ~(eq & ~zero) -> ne | zero */ 43 b.none 0b 44 45 /* Found end-of-string or inequality. */ 461: brkb p2.b, p0/z, p2.b /* find first such */ 47 lasta w0, p2, z0.b /* extract each char */ 48 lasta w1, p2, z1.b 49 sub x0, x0, x1 /* return comparison */ 50 ret 51 52 /* First fault failed: only some of the vector is valid. 53 Perform the comparison only on the valid bytes. */ 542: cmpeq p2.b, p1/z, z0.b, z1.b /* compare strings, as above */ 55 cmpne p3.b, p1/z, z0.b, 0 56 nands p2.b, p1/z, p2.b, p3.b 57 b.any 1b 58 59 /* No inequality or zero found. Re-init FFR, incr and loop. */ 60 setffr 61 incp x3, p1.b 62 b 0b 63 64 /* Found end-of-count. */ 659: mov x0, 0 /* return equal */ 66 ret 67 68 .size __strncmp_aarch64_sve, . - __strncmp_aarch64_sve 69#endif 70