Okay, #DesmetC sign-extension in (signed char -> int) promotion now works in my branch. (signed char -> long) does not work yet; it neglects to sign-extend, acting more-or-less like (unsigned char -> long). That's next to fix.

Thankfully, the codebase is small enough that it's not too hard to find the logic responsible for any given codegen decision.

Also, I came up with the trick of having the assembler backend emit comments into the output asm file. This lets me do something like printf debugging to check which codegen cases are being hit and annotate the assembly they're generating.

Naturally this is all test-driven: I'm accumulating regression tests for the broken codegen I've been fixing, and usually the way I find codegen bugs is by writing new tests expecting the mathematically correct answer, and watching them immediately fail.

#retrocomputing