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LibGfx/WebPWriter: Put hot loop in its own function

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This makes it easier to compare the generated assembly for this function
in different scenarios.

No behavior or perf change.
This commit is contained in:
Nico Weber 2024-05-08 08:22:23 -04:00 • committed by Tim Flynn
commit 1bd1b6e5e9
Notes: sideshowbarker 2024-07-17 09:56:35 +09:00
1 changed files with 23 additions and 16 deletions
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39
Userland/Libraries/LibGfx/ImageFormats/WebPWriterLossless.cpp
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@ -25,6 +25,28 @@ static bool are_all_pixels_opaque(Bitmap const& bitmap)
return true;
}
NEVER_INLINE static ErrorOr<void> write_image_data(LittleEndianOutputBitStream& bit_stream, Bitmap const& bitmap, bool all_pixels_are_opaque)
{
// This is currently the hot loop. Keep performance in mind when you change it.
for (ARGB32 pixel : bitmap) {
u8 a = pixel >> 24;
u8 r = pixel >> 16;
u8 g = pixel >> 8;
u8 b = pixel;
// We wrote a huffman table that gives every symbol 8 bits. That means we can write the image data
// out uncompressed –- but we do need to reverse the bit order of the bytes.
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[g], 8u));
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[r], 8u));
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[b], 8u));
// If all pixels are opaque, we wrote a one-element huffman table for alpha, which needs 0 bits per element.
if (!all_pixels_are_opaque)
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[a], 8u));
}
return {};
}
static ErrorOr<void> write_VP8L_image_data(Stream& stream, Bitmap const& bitmap)
{
LittleEndianOutputBitStream bit_stream { MaybeOwned<Stream>(stream) };
@ -116,22 +138,7 @@ static ErrorOr<void> write_VP8L_image_data(Stream& stream, Bitmap const& bitmap)
TRY(bit_stream.write_bits(0u, 1u)); // symbol0
// Image data.
for (ARGB32 pixel : bitmap) {
u8 a = pixel >> 24;
u8 r = pixel >> 16;
u8 g = pixel >> 8;
u8 b = pixel;
// We wrote a huffman table that gives every symbol 8 bits. That means we can write the image data
// out uncompressed –- but we do need to reverse the bit order of the bytes.
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[g], 8u));
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[r], 8u));
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[b], 8u));
// If all pixels are opaque, we wrote a one-element huffman table for alpha, which needs 0 bits per element.
if (!all_pixels_are_opaque)
TRY(bit_stream.write_bits(Compress::reverse8_lookup_table[a], 8u));
}
TRY(write_image_data(bit_stream, bitmap, all_pixels_are_opaque));
// FIXME: Make ~LittleEndianOutputBitStream do this, or make it VERIFY() that it has happened at least.
TRY(bit_stream.align_to_byte_boundary());