TODO

• Get an overview of what is implemented (and add missing to TODO)
• Fix cosimulation issues, still an issue with mem.s (now disabled)
• Change to arithmetic shift
• Have the Leros simulator as a submodule
• Use the simulator in GitHub actions (does not compile)
• Get GitHub CI green
• Restructure with one state per instruction type (like in old CA books)
• Decide on where the documentation is:
  • README here
  • Handbook on Leros
  • Leros web page
• Clarify and decide on the implementation of ldaddr
  • Morten loads form Rn, Martin from A - fixed now to Rn
• Morten’s simulator uses a single memory for all (code and data), but a dedicated register file
  • Loads .bin programs at address 0
  • Rewrite the test code for this
  • Write in the documentation about the different options
• Have a writable instruction memory (for Edu4Chip)
  • Plus a small FSM to download via serial port and deassert reset
    • Poor man’s JTAG
• Implementation and assembler test for each instruction
  • scall
  • add (test)
  • sub (test)
  • and (test)
  • or (test)
  • xor (test)
  • xori (test)
  • loadi (test for sign extension, also high versions)
  • out - needed?
  • in - needed?
  • jal
  • ldind
  • ldindh
  • ldindb/ldindh does sign extension
  • stind (offset broken now, as it counts for ldindb, test missing)
  • stindb
  • stindh
  • br (test)
  • fix backward branch
• Check if write in Chisel/Verilog is not through a register
  • wondering on timing and layout in Quartus
• Get rid of code duplication in Decode
• Do memory mapped IO
• Be able to simulate source in asm
• Setup FPGA (Nexys A7)
  • Use chipdesign1 for synthesis, OpenOCD for configuration
• get a blinking LED running
  • move it out of test to avoid breaking CI
• Memory: read in first state, write in second. Is this how we want to do it?
• Take a note on: semantic changed to have opd in words, halfword, or bytes, but address in bytes
• Looks like Morten’s simulator/compiler sign extends ldindb/h, Check it
  • and document it
• Explore Tjark’s test generation (with cosimulation)
• Use the C compiler
• Run C compiler tests
• Are half word load and stores used in the compiler?
• Any instruction not used by the compiler?
• load/store byte indirect
• Does subi sign extend? Do we need a subi? We could use addi with neg. values
• Get a simple sequential version done
• Pipelined version follows after sequential
• Run Morten’s C test programs
• gcc test suit as in Patmos
• Shouldn’t a cross-compiler have a prefix? Such as leros-clang?

Documentation

• Get text from paper into handbook, including the instruction figure
• Or in the web page

List of Instructions to be Tested

+--------+----------+
|000010-0| add      |
|000010-1| addi     |
|000011-0| sub      |
|000011-1| subi     |
|00010---| shr      |
|00011---| -        |
|00100010| and      |
|00100011| andi     |
|00100100| or       |
|00100101| ori      |
|00100110| xor      |
|00100111| xori     |
|001110-?| out      |
|000001-?| in       |
|01000---| jal      |
|01001---| -        |
+--------+----------+

Tested Instructions

+--------+----------+
|00000---| nop      |
|00100000| load     |
|00100001| loadi    |
|00101001| loadhi   |
|00101010| loadh2i  |
|00101011| loadh3i  |
|00110---| store    |
|01010---| ldaddr   |
|01100-00| ldind    |
|01100-01| ldindb   |
|01100-10| ldindh   |
|01110-00| stind    |
|01110-01| stindb   |
|01110-10| stindh   |
|1000nnnn| br       |
|1001nnnn| brz      |
|1010nnnn| brnz     |
|1011nnnn| brp      |
|1100nnnn| brn      |
|11111111| scall    |
+--------+----------+

Semantic Questions

• Do add/sub immediate sign extend? I guess so.
• Logic immediate operations shall not sign extend