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/*
* Copyright (c) 2022 Jonathan Swinney <jswinney@amazon.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/aarch64/asm.S"
function ff_pix_abs16_neon, export=1
// x0 unused
// x1 uint8_t *pix1
// x2 uint8_t *pix2
// x3 ptrdiff_t stride
// w4 int h
cmp w4, #4 // if h < 4, jump to completion section
movi v18.4S, #0 // clear result accumulator
b.lt 2f
1:
ld1 {v0.16b}, [x1], x3 // load pix1
ld1 {v4.16b}, [x2], x3 // load pix2
ld1 {v1.16b}, [x1], x3 // load pix1
ld1 {v5.16b}, [x2], x3 // load pix2
uabdl v16.8h, v0.8b, v4.8b // absolute difference accumulate
uabdl2 v17.8h, v0.16b, v4.16b
ld1 {v2.16b}, [x1], x3 // load pix1
ld1 {v6.16b}, [x2], x3 // load pix2
uabal v16.8h, v1.8b, v5.8b // absolute difference accumulate
uabal2 v17.8h, v1.16b, v5.16b
ld1 {v3.16b}, [x1], x3
ld1 {v7.16b}, [x2], x3
uabal v16.8h, v2.8b, v6.8b
uabal2 v17.8h, v2.16b, v6.16b
sub w4, w4, #4 // h -= 4
uabal v16.8h, v3.8b, v7.8b
uabal2 v17.8h, v3.16b, v7.16b
cmp w4, #4 // if h >= 4, loop
add v16.8h, v16.8h, v17.8h
uaddlv s16, v16.8h // add up everything in v16 accumulator
add d18, d16, d18 // add to the end result register
b.ge 1b
cbnz w4, 2f // if iterations remain, jump to completion section
fmov w0, s18 // copy result to general purpose register
ret
2:
ld1 {v0.16b}, [x1], x3 // load pix1
ld1 {v4.16b}, [x2], x3 // load pix2
uabdl v16.8h, v0.8b, v4.8b // absolute difference accumulate
uabal2 v16.8h, v0.16b, v4.16b
subs w4, w4, #1 // h -= 1
addv h16, v16.8h // add up v16
add d18, d16, d18 // add to result
b.ne 2b
fmov w0, s18 // copy result to general purpose register
ret
endfunc
function ff_pix_abs16_xy2_neon, export=1
// x0 unused
// x1 uint8_t *pix1
// x2 uint8_t *pix2
// x3 ptrdiff_t stride
// w4 int h
add x5, x2, x3 // use x5 to hold uint8_t *pix3
movi v0.2d, #0 // initialize the result register
// Load initial pix2 values for either the unrolled version or completion version.
ldur q4, [x2, #1] // load pix2+1
ldr q3, [x2] // load pix2
uaddl v2.8h, v4.8b, v3.8b // pix2 + pix2+1 0..7
uaddl2 v3.8h, v4.16b, v3.16b // pix2 + pix2+1 8..15
cmp w4, #4 // if h < 4 jump to the completion version
b.lt 2f
1:
// This is an unrolled implementation. It completes 4 iterations of the C for each branch.
// In each iteration, pix2[i+1] == pix3[i]. This means we need only three loads per iteration,
// plus two at the beginning to start.
ldur q5, [x5, #1] // load pix3+1
ld1 {v4.16b}, [x5], x3 // load pix3
ld1 {v1.16b}, [x1], x3 // load pix1
ldur q7, [x5, #1] // load pix3+1
ld1 {v6.16b}, [x5], x3 // load pix3
ld1 {v16.16b}, [x1], x3 // load pix1
ldur q19, [x5, #1] // load pix3+1
ld1 {v18.16b}, [x5], x3 // load pix3
ld1 {v17.16b}, [x1], x3 // load pix1
ldur q22, [x5, #1] // load pix3+1
ld1 {v21.16b}, [x5], x3 // load pix3
ld1 {v20.16b}, [x1], x3 // load pix1
// These blocks compute the average: avg(pix2[n], pix2[n+1], pix3[n], pix3[n+1])
uaddl v30.8h, v4.8b, v5.8b // pix3 + pix3+1 0..7
uaddl2 v31.8h, v4.16b, v5.16b // pix3 + pix3+1 8..15
add v23.8h, v2.8h, v30.8h // add up 0..7, using pix2 + pix2+1 values from previous iteration
add v24.8h, v3.8h, v31.8h // add up 8..15, using pix2 + pix2+1 values from previous iteration
rshrn v23.8b, v23.8h, #2 // shift right 2 0..7 (rounding shift right)
rshrn2 v23.16b, v24.8h, #2 // shift right 2 8..15
uaddl v2.8h, v6.8b, v7.8b // pix3 + pix3+1 0..7
uaddl2 v3.8h, v6.16b, v7.16b // pix3 + pix3+1 8..15
add v26.8h, v30.8h, v2.8h // add up 0..7, using pix2 + pix2+1 values from pix3 above
add v27.8h, v31.8h, v3.8h // add up 8..15, using pix2 + pix2+1 values from pix3 above
rshrn v26.8b, v26.8h, #2 // shift right 2 0..7 (rounding shift right)
rshrn2 v26.16b, v27.8h, #2 // shift right 2 8..15
uaddl v4.8h, v18.8b, v19.8b // pix3 + pix3+1 0..7
uaddl2 v5.8h, v18.16b, v19.16b // pix3 + pix3+1 8..15
add v28.8h, v2.8h, v4.8h // add up 0..7, using pix2 + pix2+1 values from pix3 above
add v29.8h, v3.8h, v5.8h // add up 8..15, using pix2 + pix2+1 values from pix3 above
rshrn v28.8b, v28.8h, #2 // shift right 2 0..7 (rounding shift right)
rshrn2 v28.16b, v29.8h, #2 // shift right 2 8..15
uaddl v2.8h, v21.8b, v22.8b // pix3 + pix3+1 0..7
uaddl2 v3.8h, v21.16b, v22.16b // pix3 + pix3+1 8..15
add v30.8h, v4.8h, v2.8h // add up 0..7, using pix2 + pix2+1 values from pix3 above
add v31.8h, v5.8h, v3.8h // add up 8..15, using pix2 + pix2+1 values from pix3 above
rshrn v30.8b, v30.8h, #2 // shift right 2 0..7 (rounding shift right)
rshrn2 v30.16b, v31.8h, #2 // shift right 2 8..15
// Averages are now stored in these registers:
// v23, v16, v28, v30
// pix1 values in these registers:
// v1, v16, v17, v20
// available:
// v4, v5, v7, v18, v19, v24, v25, v27, v29, v31
sub w4, w4, #4 // h -= 4
// Using absolute-difference instructions instead of absolute-difference-accumulate allows
// us to keep the results in 16b vectors instead of widening values with twice the instructions.
// This approach also has fewer data dependencies, allowing better instruction level parallelism.
uabd v4.16b, v1.16b, v23.16b // absolute difference 0..15, i=0
uabd v5.16b, v16.16b, v26.16b // absolute difference 0..15, i=1
uabd v6.16b, v17.16b, v28.16b // absolute difference 0..15, i=2
uabd v7.16b, v20.16b, v30.16b // absolute difference 0..15, i=3
cmp w4, #4 // loop if h >= 4
// Now add up all the values in each vector, v4-v7 with widening adds
uaddl v19.8h, v4.8b, v5.8b
uaddl2 v18.8h, v4.16b, v5.16b
uaddl v4.8h, v6.8b, v7.8b
uaddl2 v5.8h, v6.16b, v7.16b
add v4.8h, v4.8h, v5.8h
add v4.8h, v4.8h, v18.8h
add v4.8h, v4.8h, v19.8h
uaddlv s4, v4.8h // finish adding up accumulated values
add d0, d0, d4 // add the value to the top level accumulator
b.ge 1b
cbnz w4, 2f // if iterations remain jump to completion section
fmov w0, s0 // copy result to general purpose register
ret
2:
// v2 and v3 are set either at the end of this loop or at from the unrolled version
// which branches here to complete iterations when h % 4 != 0.
ldur q5, [x5, #1] // load pix3+1
ld1 {v4.16b}, [x5], x3 // load pix3
ld1 {v1.16b}, [x1], x3 // load pix1
subs w4, w4, #1 // decrement h
uaddl v18.8h, v4.8b, v5.8b // pix3 + pix3+1 0..7
uaddl2 v19.8h, v4.16b, v5.16b // pix3 + pix3+1 8..15
add v16.8h, v2.8h, v18.8h // add up 0..7, using pix2 + pix2+1 values from previous iteration
add v17.8h, v3.8h, v19.8h // add up 8..15, using pix2 + pix2+1 values from previous iteration
// divide by 4 to compute the average of values summed above
urshr v16.8h, v16.8h, #2 // shift right by 2 0..7 (rounding shift right)
urshr v17.8h, v17.8h, #2 // shift right by 2 8..15
uxtl2 v8.8h, v1.16b // 8->16 bits pix1 8..15
uxtl v1.8h, v1.8b // 8->16 bits pix1 0..7
uabd v6.8h, v1.8h, v16.8h // absolute difference 0..7
uaba v6.8h, v8.8h, v17.8h // absolute difference accumulate 8..15
mov v2.16b, v18.16b // pix3 -> pix2
mov v3.16b, v19.16b // pix3+1 -> pix2+1
uaddlv s6, v6.8h // add up accumulator in v6
add d0, d0, d6 // add to the final result
b.ne 2b // loop if h > 0
fmov w0, s0 // copy result to general purpose register
ret
endfunc
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