1 /* 2 * strncmp - compare two strings with limit 3 * 4 * Copyright (c) 2018-2021, Arm Limited. 5 * SPDX-License-Identifier: MIT 6 */ 7 8 #include "../asmdefs.h" 9 10 #if __ARM_FEATURE_SVE 11 /* Assumptions: 12 * 13 * ARMv8-a, AArch64 14 * SVE Available. 15 */ 16 17 ENTRY (__strncmp_aarch64_sve) 18 PTR_ARG (0) 19 PTR_ARG (1) 20 SIZE_ARG (2) 21 setffr /* initialize FFR */ 22 mov x3, 0 /* initialize off */ 23 24 0: whilelo p0.b, x3, x2 /* while off < max */ 25 b.none 9f 26 27 ldff1b z0.b, p0/z, [x0, x3] 28 ldff1b z1.b, p0/z, [x1, x3] 29 rdffrs p1.b, p0/z 30 b.nlast 2f 31 32 /* First fault did not fail: the vector up to max is valid. 33 Avoid depending on the contents of FFR beyond the branch. 34 Increment for a whole vector, even if we've only read a partial. 35 This is significantly cheaper than INCP, and since OFF is not 36 used after the loop it is ok to increment OFF past MAX. */ 37 incb x3 38 cmpeq p1.b, p0/z, z0.b, z1.b /* compare strings */ 39 cmpne p2.b, p0/z, z0.b, 0 /* search for ~zero */ 40 nands p2.b, p0/z, p1.b, p2.b /* ~(eq & ~zero) -> ne | zero */ 41 b.none 0b 42 43 /* Found end-of-string or inequality. */ 44 1: brkb p2.b, p0/z, p2.b /* find first such */ 45 lasta w0, p2, z0.b /* extract each char */ 46 lasta w1, p2, z1.b 47 sub x0, x0, x1 /* return comparison */ 48 ret 49 50 /* First fault failed: only some of the vector is valid. 51 Perform the comparison only on the valid bytes. */ 52 2: cmpeq p2.b, p1/z, z0.b, z1.b /* compare strings, as above */ 53 cmpne p3.b, p1/z, z0.b, 0 54 nands p2.b, p1/z, p2.b, p3.b 55 b.any 1b 56 57 /* No inequality or zero found. Re-init FFR, incr and loop. */ 58 setffr 59 incp x3, p1.b 60 b 0b 61 62 /* Found end-of-count. */ 63 9: mov x0, 0 /* return equal */ 64 ret 65 66 END (__strncmp_aarch64_sve) 67 68 #endif 69 70