| Time |
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| 00:30 |
cheapie |
3336 lines of code to make a glowlight flash once per second has to be some kind of record |
| 00:31 |
cheapie |
3308 of that is Lua, the rest is RISC-V assembly |
| 00:32 |
user333_ |
why do it in a simple way when you could do it like that? |
| 00:33 |
cheapie |
FWIW this is the assembly part: https://gist.github.com/cheapie/45406dabdd7d031859caf6a1832a1675 |
| 00:33 |
* user333_ |
pretends to know RISC-V assembly |
| 00:33 |
user333_ |
nice code |
| 00:35 |
cheapie |
1-4 set up the MMIO region and configure pins B and D as output (also turning the output on), 7-11 is hopefully self-explanatory, 12-13 waits for the blinky plant (on one of the other pins) to blink, 14 jumps back to 6 to restart the loop when it does |
| 00:35 |
cheapie |
17-19 load the current mesecons I/O values, toggle pins B and D, then write them back |
| 00:36 |
user333_ |
ah |
| 00:36 |
cheapie |
25 does the sleeping between flashes (the ones where it's not waiting for the blinky plant), 26-27 make it run line 25 13 times (the 13 comes from line 23) before it returns |
| 00:38 |
cheapie |
Lines 12-13 are the ones I'm most proud of - they're borrowed from my digital sign thing and are my favorite way to wait for a mesecons input to change on RVController, provided I don't care which input it is |
| 00:38 |
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| 00:39 |
user333_ |
i assume assembly becomes much easier once you know all the keywords |
| 00:39 |
cheapie |
The lr.w on line 12 is a "load reserved" from Zalrsc (part of A), it basically means "read the data from this memory address and then keep an eye on it to see if anyone else changes it". Normally you would pair it with an sc.w (store conditional), which is "write this data to this memory address, but ONLY if nobody touched it since the lr.w" |
| 00:39 |
cheapie |
yes |
| 00:40 |
user333_ |
otherwise it just looks like little clumps of letters |
| 00:40 |
cheapie |
In this case I'm instead pairing the lr.w with a wrs.nto (wait for reservation set, no timeout), which is from Zawrs and means "halt until someone touches the memory I did an lr.w on" |
| 00:42 |
user333_ |
makes me respect the work C compilers do to translate easily human-readable code into lower-level assembly |
| 00:43 |
cheapie |
Really even just knowing what the instruction abbreviations expand to helps a lot. li = load immediate, csrw = CSR write, sh = store halfword, call = (take a guess), lr.w = load-reserved word, wrs.nto = wait on reservation set, no timeout, j = jump, lb = load byte, xori = XOR with immediate, sb = store byte, ret = return, pause = ...pause, addi = add immediate, bnez = branch if not equal to zero |
| 00:45 |
cheapie |
li, csrw, call, j, ret, and bnez there are pseudoinstructions, most likely expanding in this case to: lui+addi, csrrw, jal, jal, jalr, and bne respectively |
| 00:46 |
user333_ |
is there any real reason that assembly uses such abbreviated keywords? |
| 00:47 |
cheapie |
Less tedious to type is probably the big one at this point |
| 00:47 |
user333_ |
true |
| 00:48 |
user333_ |
though not many people write assembly these days (aside from very low level stuff) so it doesn't matter *too* much |
| 00:48 |
cheapie |
Like I'd much rather type "sh t1,0(s0)" as opposed to "storeHalfWord(temporaryRegister1,savedRegister0,0)" |
| 00:50 |
cheapie |
Modern amd64 has instruction names like "VCVTTPD2UQQ", I'd really hate to have to type the full name of _that_ out |
| 00:51 |
user333_ |
reminds me of when i picked up writing bash (well, POSIX shell usually), lots of unintuitive things |
| 00:53 |
* cheapie |
gives user333_ https://www.cs.sfu.ca/~ashriram/Courses/CS295/assets/notebooks/RISCV/RISCV_CARD.pdf |
| 00:54 |
cheapie |
RVController is RV32IMACB and therefore supports every instruction in there except for the F/D stuff on page 2 (and therefore also the corresponding pseudoinstructions on page 4) |
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MinetestBot |
[git] CodingMantisUA -> luanti-org/luanti: HUD inventory: allow custom background per element (#17359) b4eb8b9 https://github.com/luanti-org/luanti/commit/b4eb8b91e611c3d83f7557c39b4f1caab9406e57 (2026-09-18T13:41:38Z) |
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* cheapie |
hmms at https://www.reddit.com/r/StVO/comments/1goslcm/motor_abstellen/ for a bit, makes https://cheapiesystems.com/media/images/screenshot_20260918_111129.png |
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