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buffer map permeates zero init now in any case

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This commit is contained in:
Andreas Reich 2021-01-23 09:57:55 +01:00
parent a51b4f9232
commit 076aecd150
1 changed files with 13 additions and 12 deletions
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25
wgpu-core/src/device/mod.rs
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@ -196,27 +196,28 @@ fn map_buffer<B: hal::Backend>(
}),
_ => None,
};
let writes_are_synced = buffer.sync_mapped_writes.is_some() || block.is_coherent();
// Zero out uninitialized parts of the mapping. (Spec dictates all resources behave as if they were initialized with zero)
// Note that going through a `fill_buffer` command may be faster but we don't have the chance of interacting with the queue
// between map intent (map_buffer_async or immediately) and this call.
//
// If this is a read mapping, ideally we would use a `fill_buffer` command before reading the data from GPU (i.e. `invalidate_range`).
// However, this would require us to kick off and wait for a command buffer or piggy back on an existing one (the later is likely the only worthwhile option).
// As reading uninitialized memory isn't a particular important path to support,
// we instead just initialize the memory here and make sure it is GPU visible, so this happens at max only once for every buffer region.
//
// If this is a write mapping zeroing out the memory here is the only reasonable way as all data is pushed to GPU anyways.
let zero_init_needs_flush_now = !block.is_coherent() && buffer.sync_mapped_writes.is_none(); // No need to flush if it is flushed later anyways.
let uninitialized_ranges: Vec<Range<BufferAddress>> =
buffer.uninitialized_ranges_in_range(Range {
start: offset,
end: offset + size,
});
for range in uninitialized_ranges {
unsafe {
ptr::write_bytes(
ptr.as_ptr().offset(range.start as isize),
0,
(range.end - range.start) as usize,
)
};
let size = (range.end - range.start) as usize;
unsafe { ptr::write_bytes(ptr.as_ptr().offset(range.start as isize), 0, size) };
// (technically the buffer is only initialized when we're done unmapping but we know it can't be used otherwise meanwhile)
if writes_are_synced {
buffer.mark_initialized(range);
if zero_init_needs_flush_now {
block.flush_range(raw, range.start, Some(size))?;
}
}