Optimized _TransparentPlot_ASM for speed* #28
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Unrolled each of the opaque and transparent braches into four iterations, so stretches of the same pixel opaqueness/transparency mostly fall through the jumps and execute faster. Before (12 bytes): * opaque->opaque: 41 cc * opaque->trans: 36 cc * trans->opaque: 46 cc * trans->trans: 41 cc After (54 bytes; lists cycles after 1/2/3/4 mod 4 iterations in a row of previous pixel state): * opaque->opaque: 36/36/36/41 cc * opaque->trans: 41/41/41/36 cc * trans->opaque: 38/38/38/46 cc * trans->trans: 33/33/33/38 cc Starts on the fast transparent path based on the assumption that the majority of transparent sprite pixel rows start with a transparent pixel, as transparency is often used to draw "cutout" images.
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Untested; would appreciate if someone could at least take a second look and check that it looks reasonable. |
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Thanks! :) |
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For the record: @mateoconlechuga tested this with an example program using transparent sprites and said that it worked. |
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Unrolled each of the opaque and transparent braches into four iterations, so stretches of the same pixel opaqueness/transparency mostly fall through the jumps and execute faster.
Before (12 bytes):
After (54 bytes; lists cycles after 1/2/3/4 mod 4 iterations in a row of previous pixel state):
Starts on the fast transparent path based on the assumption that the majority of transparent sprite pixel rows start with a transparent pixel, as transparency is often used to draw "cutout" images.