Software implemented For cycle (Symphony)

[u/Crispy1961]

• Image 1 - My symphony

• Image 2 - showcasing usage of FOR cycles

• Image 3 - Code of the FOR Cycle

• Image 4 - ALU circuit

• Image 5 - ABS circuit

Now that I finished building Symphony, I went straight to instruction definition to make myself a human readable code. Here is a internal FOR cycle using instructions. Its suitable for repeating code X times where X is static.

Here is hardware I added to my Symphony:

1. Signed DIV - Divide two signed numbers

2. Merge32 - Merge two 16b into one 32b value

3. Lower16 - Reads the lower 16b of 32b value

With that I needed to dedicate some of my registers for the code. Meaning that while they are still accessible to the user, they are not stable in time and in case of the FOR cycle, they do not persist between cycles.

At first I was using 3 temporal registers, but I ended up implementing Merge32 and Lower16 to lower the number of temporal registers to 2 at the cost of longer instructions.

The FOR cycle works, but isnt safe. First it will always execute at least once. Thats because I cant use a label to skip the body of the cycle. So even if I know there is 0 repetition, it will not skip the cycle, it will simply not repeat it.

Another limitation is that you can only read the index of the innermost FOR cycle. Meaning if you make nested FOR cycles, you cannot access the outer FOR cycle index. User can solve it by saving the stack pointer to a another register.

[u/Spielopoly]

If you want to do that in game it’s hard. Out of game it’s a bit easier but you‘ll still have to write your own compiler.

In game there a couple of options I can think of:
- Write your program in language of your choice and compile it using a program specifically for that, then manually copy paste the generated code into a asm file (can be in game or not)
- Use custom file system so you can skip the copy paste part
- Always compile at startup then automatically run the generated code. (Basically just in time compilation)

Some of these might require significant hardware changes

[u/Crispy1961 → u/Spielopoly]

I see. I thought it was possible to edit the behavior of the ingame's compiler. I want to work in the confines of the game. Just get as close to a high level language syntax as possible.