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perf: fn rav1d_prepare_intra_edges: pre-slice #1415

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perf: fn rav1d_prepare_intra_edges: pre-slice #1415

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69df003
perf improvement re: issue #1394
ERobsham May 25, 2025
46e6d7e
fixes + suggestion from PR
ERobsham May 25, 2025
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52 changes: 47 additions & 5 deletions src/ipred_prepare.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -186,6 +186,8 @@ pub fn rav1d_prepare_intra_edges<BD: BitDepth>(

let bitdepth = bd.bitdepth();
let stride = dst.pixel_stride::<BD>();
let is_neg_stride = 0 > stride;
let abs_stride = stride.unsigned_abs();

match mode {
VERT_PRED..=VERT_LEFT_PRED => {
Expand Down Expand Up @@ -245,8 +247,28 @@ pub fn rav1d_prepare_intra_edges<BD: BitDepth>(
let left = &mut topleft_out[topleft_out_offset - sz..];
if have_left {
let px_have = cmp::min(sz, (h - y << 2) as usize);
for i in 0..px_have {
left[sz - 1 - i] = *(dst + (i as isize * stride - 1)).index::<BD>();
{
let slice_offset = if is_neg_stride {
(px_have - 1) as isize * stride
} else {
0
};
let dst_slice =
&*(dst + slice_offset - 1isize).slice::<BD>((px_have - 1) * abs_stride + 1);
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@kkysen kkysen May 26, 2025

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The slice here overlaps ones from other threads, as the individual indices accessed are interleaved. That's why .index::<BD>() works, but not a single .slice::<BD>(). It's unfortunately a very tricky problem.


// SAFETY: We've already implcitly bounds checked with the `slice()` call.
// We can safely avoid any bounds-checking overhead now.
if is_neg_stride {
for i in 0..px_have {
left[sz - 1 - i] = *unsafe {
dst_slice.get_unchecked(((px_have - 1) * abs_stride) - (i * abs_stride))
};
}
} else {
for i in 0..px_have {
left[sz - 1 - i] = *unsafe { dst_slice.get_unchecked(i * abs_stride) }
}
}
}
if px_have < sz {
BD::pixel_set(left, left[sz - px_have], sz - px_have);
Expand Down Expand Up @@ -274,9 +296,29 @@ pub fn rav1d_prepare_intra_edges<BD: BitDepth>(
};
if have_bottomleft {
let px_have = cmp::min(sz, (h - y - th << 2) as usize);
for i in 0..px_have {
bottom_left[sz - 1 - i] =
*(dst + ((sz + i) as isize * stride - 1)).index::<BD>();
{
let slice_offset = if is_neg_stride {
(px_have - 1 + sz) as isize * stride
} else {
(sz * abs_stride) as isize
};
let dst_slice =
&*(dst + slice_offset - 1isize).slice::<BD>((px_have - 1) * abs_stride + 1);
// SAFETY: We've already implcitly bounds checked with the `slice()` call.
// We can safely avoid any bounds-checking overhead now.
if is_neg_stride {
for i in 0..px_have {
bottom_left[sz - 1 - i] = *unsafe {
dst_slice
.get_unchecked(((px_have - 1) * abs_stride) - (i * abs_stride))
};
}
} else {
for i in 0..px_have {
bottom_left[sz - 1 - i] =
*unsafe { dst_slice.get_unchecked(i * abs_stride) }
}
}
}
if px_have < sz {
BD::pixel_set(bottom_left, bottom_left[sz - px_have], sz - px_have);
Expand Down
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