diff options
Diffstat (limited to 'lib/libc/aarch64/string/strlen.S')
| -rw-r--r-- | lib/libc/aarch64/string/strlen.S | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/lib/libc/aarch64/string/strlen.S b/lib/libc/aarch64/string/strlen.S new file mode 100644 index 000000000000..6fefc252eca1 --- /dev/null +++ b/lib/libc/aarch64/string/strlen.S @@ -0,0 +1,45 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 2024 Getz Mikalsen <getz@FreeBSD.org> +*/ + +#include <machine/asm.h> + + .weak strlen + .set strlen, __strlen + .text + +ENTRY(__strlen) + bic x10, x0, #0xf // aligned src + and x9, x0, #0xf + ldr q0, [x10] + cmeq v0.16b, v0.16b, #0 + shrn v0.8b, v0.8h, #4 + fmov x1, d0 + cbz x9, .Laligned + lsl x2, x0, #2 // get the byte offset + lsr x1, x1, x2 // shift by offset index + cbz x1, .Lloop + rbit x1, x1 + clz x0, x1 + lsr x0, x0, #2 + ret + +.Laligned: + cbnz x1, .Ldone + +.Lloop: + ldr q0, [x10, #16]! + cmeq v0.16b, v0.16b, #0 + shrn v0.8b, v0.8h, #4 // reduce to fit mask in GPR + fmov x1, d0 + cbz x1, .Lloop +.Ldone: + sub x0, x10, x0 + rbit x1, x1 // reverse bits as NEON has no ctz + clz x3, x1 + lsr x3, x3, #2 + add x0, x0, x3 + ret +END(__strlen) |