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