diff options
Diffstat (limited to 'contrib/arm-optimized-routines/string/aarch64/strnlen.S')
| -rw-r--r-- | contrib/arm-optimized-routines/string/aarch64/strnlen.S | 62 |
1 files changed, 25 insertions, 37 deletions
diff --git a/contrib/arm-optimized-routines/string/aarch64/strnlen.S b/contrib/arm-optimized-routines/string/aarch64/strnlen.S index 48d2495d2082..6a96ec268f1a 100644 --- a/contrib/arm-optimized-routines/string/aarch64/strnlen.S +++ b/contrib/arm-optimized-routines/string/aarch64/strnlen.S @@ -1,8 +1,8 @@ /* * strnlen - calculate the length of a string with limit. * - * 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 cntin x1 @@ -20,39 +20,28 @@ #define src x2 #define synd x3 #define shift x4 -#define wtmp w4 #define tmp x4 #define cntrem x5 #define qdata q0 #define vdata v0 #define vhas_chr v1 -#define vrepmask v2 -#define vend v3 -#define dend d3 +#define vend v2 +#define dend d2 /* 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. */ + Process the string in 16-byte aligned chunks. Compute a 64-bit mask with + four bits per byte using the shrn instruction. A count trailing zeros then + identifies the first zero byte. */ ENTRY (__strnlen_aarch64) - PTR_ARG (0) - SIZE_ARG (1) bic src, srcin, 15 - mov wtmp, 0xf00f cbz cntin, L(nomatch) - ld1 {vdata.16b}, [src], 16 - dup vrepmask.8h, wtmp + ld1 {vdata.16b}, [src] cmeq vhas_chr.16b, vdata.16b, 0 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) @@ -64,37 +53,40 @@ L(finish): csel result, cntin, result, ls ret +L(nomatch): + mov result, cntin + ret + L(start_loop): sub tmp, src, srcin + 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 5 L(loop32): - ldr qdata, [src], 16 + ldr qdata, [src, 32]! cmeq vhas_chr.16b, vdata.16b, 0 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 + ldr qdata, [src, 16] subs cntrem, cntrem, 32 cmeq vhas_chr.16b, vdata.16b, 0 - b.ls L(end) + 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 */ - sub src, src, 16 - mov synd, vend.d[0] + shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */ sub result, src, srcin + fmov synd, dend #ifndef __AARCH64EB__ rbit synd, synd #endif @@ -104,9 +96,5 @@ L(end): csel result, cntin, result, ls ret -L(nomatch): - mov result, cntin - ret - END (__strnlen_aarch64) |