Dragon MOOH video optimisations #1137
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
added 2 commits
January 12, 2025 14:01
Save 1 byte and 4 cycles computing address within font. Any TFR between index registers can be optimised so long as current Z flag is not used (and even then if the destination is U or S). e.g. TFR X,U ; 2 bytes, 6 cycles ; becomes: LEAU ,X ; 2 bytes, 4 cycles Use the B register within plot_fast to make some savings. Add 128 to destination screen address in Y so that subsequent offsest are 8-bit. Same 128 byte offset in m6847_clear_across, as well as opportunistically using a post-increment to avoid the need for LEAX 1,X. Same 128 byte offset in m6847_cursor_on/off. In m6847_scroll_up/down, use stack ops with U instead of predec/postinc.
Use LSLB instead of ROLB in the fast multiply by 8 in m6847_plot_char. AFAICT the carry flag isn't necessarily cleared before plot_char() hands off to m6847_plot_char. If it were set on entry, the index into the font would be offset by 1. I've never seen that happen, but this fix costs nothing.
|
Thanks |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Optimise TFR usage similar to coco3 patch.
Save 1 byte and 4 cycles computing address within font.
Use the B register within plot_fast to make some savings. Add 128 to
destination screen address in Y so that subsequent offsest are 8-bit.
Same 128 byte offset in m6847_clear_across, as well as opportunistically
using a post-increment to avoid the need for LEAX 1,X.
Same 128 byte offset in m6847_cursor_on/off.
In m6847_scroll_up/down, use stack ops with U instead of predec/postinc.
Also, fix a possible (maybe not now, but in the future) font corruption;
use LSLB instead of ROLB in fast multiply by 8.