diff options
Diffstat (limited to 'string/aarch64/strchrnul-mte.S')
| -rw-r--r-- | string/aarch64/strchrnul-mte.S | 47 |
1 files changed, 24 insertions, 23 deletions
diff --git a/string/aarch64/strchrnul-mte.S b/string/aarch64/strchrnul-mte.S index 1b0d0a6..543ee88 100644 --- a/string/aarch64/strchrnul-mte.S +++ b/string/aarch64/strchrnul-mte.S @@ -1,8 +1,8 @@ /* * strchrnul - find a character or nul in a string * - * Copyright (c) 2020, Arm Limited. - * SPDX-License-Identifier: MIT + * Copyright (c) 2020-2022, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception */ /* Assumptions: @@ -11,7 +11,7 @@ * MTE compatible. */ -#include "../asmdefs.h" +#include "asmdefs.h" #define srcin x0 #define chrin w1 @@ -20,38 +20,32 @@ #define src x2 #define tmp1 x1 #define tmp2 x3 -#define tmp2w w3 #define vrepchr v0 #define vdata v1 #define qdata q1 #define vhas_nul v2 #define vhas_chr v3 -#define vrepmask v4 -#define vend v5 -#define dend d5 +#define vend v4 +#define dend d4 -/* Core algorithm: - - For each 16-byte chunk we calculate a 64-bit syndrome value with four bits - per byte. For even bytes, bits 0-3 are set if the relevant byte matched the - requested character or the byte is NUL. Bits 4-7 must be zero. Bits 4-7 are - set likewise for odd bytes so that adjacent bytes can be merged. Since the - bits in the syndrome reflect the order in which things occur in the original - string, counting trailing zeros identifies exactly which byte matched. */ +/* + Core algorithm: + For each 16-byte chunk we calculate a 64-bit nibble mask value with four bits + per byte. We take 4 bits of every comparison byte with shift right and narrow + by 4 instruction. Since the bits in the nibble mask reflect the order in + which things occur in the original string, counting leading zeros identifies + exactly which byte matched. */ ENTRY (__strchrnul_aarch64_mte) PTR_ARG (0) bic src, srcin, 15 dup vrepchr.16b, chrin ld1 {vdata.16b}, [src] - mov tmp2w, 0xf00f - dup vrepmask.8h, tmp2w cmeq vhas_chr.16b, vdata.16b, vrepchr.16b cmhs vhas_chr.16b, vhas_chr.16b, vdata.16b lsl tmp2, srcin, 2 - and vhas_chr.16b, vhas_chr.16b, vrepmask.16b - addp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ + shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */ fmov tmp1, dend lsr tmp1, tmp1, tmp2 /* Mask padding bits. */ cbz tmp1, L(loop) @@ -63,15 +57,22 @@ ENTRY (__strchrnul_aarch64_mte) .p2align 4 L(loop): - ldr qdata, [src, 16]! + ldr qdata, [src, 16] + cmeq vhas_chr.16b, vdata.16b, vrepchr.16b + cmhs vhas_chr.16b, vhas_chr.16b, vdata.16b + umaxp vend.16b, vhas_chr.16b, vhas_chr.16b + fmov tmp1, dend + cbnz tmp1, L(end) + ldr qdata, [src, 32]! cmeq vhas_chr.16b, vdata.16b, vrepchr.16b cmhs vhas_chr.16b, vhas_chr.16b, vdata.16b umaxp vend.16b, vhas_chr.16b, vhas_chr.16b fmov tmp1, dend cbz tmp1, L(loop) - - and vhas_chr.16b, vhas_chr.16b, vrepmask.16b - addp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ + sub src, src, 16 +L(end): + shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */ + add src, src, 16 fmov tmp1, dend #ifndef __AARCH64EB__ rbit tmp1, tmp1 |