diff options
Diffstat (limited to 'sysdeps/aarch64/memchr.S')
| -rw-r--r-- | sysdeps/aarch64/memchr.S | 25 |
1 files changed, 9 insertions, 16 deletions
diff --git a/sysdeps/aarch64/memchr.S b/sysdeps/aarch64/memchr.S index b060eee97d..2053a977b6 100644 --- a/sysdeps/aarch64/memchr.S +++ b/sysdeps/aarch64/memchr.S @@ -41,24 +41,21 @@ #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) PTR_ARG (0) @@ -67,12 +64,9 @@ ENTRY (MEMCHR) 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) @@ -111,8 +105,7 @@ L(loop32_2): fmov synd, dend cbz synd, L(loop32) 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 */ fmov synd, dend add tmp, srcin, cntin sub cntrem, tmp, src |