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