diff options
Diffstat (limited to 'string/aarch64/memchr-mte.S')
| -rw-r--r-- | string/aarch64/memchr-mte.S | 58 |
1 files changed, 26 insertions, 32 deletions
diff --git a/string/aarch64/memchr-mte.S b/string/aarch64/memchr-mte.S index c2e967d..948c3cb 100644 --- a/string/aarch64/memchr-mte.S +++ b/string/aarch64/memchr-mte.S @@ -1,8 +1,8 @@ /* * memchr - find a character in a memory zone * - * 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 @@ -23,25 +23,21 @@ #define synd x5 #define shift x6 #define tmp x7 -#define wtmp w7 #define vrepchr v0 #define qdata q1 #define vdata v1 #define vhas_chr v2 -#define vrepmask v3 -#define vend v4 -#define dend d4 +#define vend v3 +#define dend d3 /* 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. */ + 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 (__memchr_aarch64_mte) PTR_ARG (0) @@ -50,55 +46,53 @@ ENTRY (__memchr_aarch64_mte) cbz cntin, L(nomatch) ld1 {vdata.16b}, [src] dup vrepchr.16b, chrin - mov wtmp, 0xf00f - dup vrepmask.8h, wtmp cmeq vhas_chr.16b, vdata.16b, vrepchr.16b lsl shift, 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 synd, dend lsr synd, synd, shift cbz synd, L(start_loop) rbit synd, synd clz synd, synd - add result, srcin, synd, lsr 2 cmp cntin, synd, lsr 2 + add result, srcin, synd, lsr 2 csel result, result, xzr, hi ret + .p2align 3 L(start_loop): sub tmp, src, srcin - add tmp, tmp, 16 + add tmp, tmp, 17 subs cntrem, cntin, tmp - b.ls L(nomatch) + b.lo L(nomatch) /* Make sure that it won't overread by a 16-byte chunk */ - add tmp, cntrem, 15 - tbnz tmp, 4, L(loop32_2) - + tbz cntrem, 4, L(loop32_2) + sub src, src, 16 .p2align 4 L(loop32): - ldr qdata, [src, 16]! + ldr qdata, [src, 32]! cmeq vhas_chr.16b, vdata.16b, vrepchr.16b umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ fmov synd, dend cbnz synd, L(end) L(loop32_2): - ldr qdata, [src, 16]! - subs cntrem, cntrem, 32 + ldr qdata, [src, 16] cmeq vhas_chr.16b, vdata.16b, vrepchr.16b - b.ls L(end) + subs cntrem, cntrem, 32 + b.lo L(end_2) umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ fmov synd, dend cbz synd, L(loop32) +L(end_2): + add src, src, 16 L(end): - 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 */ + sub cntrem, src, srcin fmov synd, dend - add tmp, srcin, cntin - sub cntrem, tmp, src + sub cntrem, cntin, cntrem #ifndef __AARCH64EB__ rbit synd, synd #endif |