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/*
* Copyright © 2024 Rémi Denis-Courmont.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "libavutil/riscv/asm.S"
.macro lx rd, addr
#if (__riscv_xlen == 32)
lw \rd, \addr
#elif (__riscv_xlen == 64)
ld \rd, \addr
#else
lq \rd, \addr
#endif
.endm
func ff_startcode_find_candidate_rvb, zbb
lpad 0
add a1, a0, a1
// Potentially unaligned head
andi t0, a0, -(__riscv_xlen / 8)
beq a0, a1, 2f
andi t1, a0, (__riscv_xlen / 8) - 1
lx t2, (t0)
li t3, __riscv_xlen
orc.b t2, t2
slli t1, t1, 3
not t2, t2
sub t3, t3, t1
srl t2, t2, t1
addi t0, t0, __riscv_xlen / 8
sll t2, t2, t1
bnez t2, 4f
// Main loop (including potentially short tail)
bge t0, a1, 2f
li t3, -1
1:
lx t2, (t0)
addi t0, t0, __riscv_xlen / 8
orc.b t2, t2
bne t2, t3, 3f // t2 != -1 iff (at least one) zero byte
blt t0, a1, 1b
2: // No zero byte found
sub a0, a1, a0
ret
3: // Zero byte found in main loop
not t2, t2
4: // Zero byte found in head
ctz t2, t2
addi t0, t0, -(__riscv_xlen / 8) // back-track
srl t2, t2, 3
add t0, t0, t2
// Uncomment the following line for exact POSIX C strnlen() semantics.
//minu t0, t0, a1 // ignore zero byte in tail
sub a0, t0, a0
ret
endfunc
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