#DesmetC (signed char -> long) promotion is now working on my branch: got it on the first try, which hopefully means I'm internalizing the codebase. Now I will start on tests for mixed-sign arithmetic.
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#DesmetC (signed char -> long) promotion is now working on my branch: got it on the first try, which hopefully means I'm internalizing the codebase. Now I will start on tests for mixed-sign arithmetic.
It's been a pretty productive night in the ol' #DesmetC codebase. Regression tests finally checked in, all the mixed-size integer addition/subtraction involving signed chars I could think of is exercised and passing, nice.
Then I try i8 * i8 -> int and it instantly breaks, not so nice 🫠.
Oh well, that gives me something to fix tomorrow.
Also, I haven't ventured into floating point conversion land yet, either. I'm sure that'll have plenty of dragons when used with signed char.
All this is making me appreciate the wisdom of BCPL and B who have just a word-sized type -- or #Forth which takes that and adds char, as a treat.
Oh gosh
MOV CL,BYTE [BP-2]
XCHG CX,AX
CBW
XCHG CX,AX
XCHG CX,AX
CBW
XCHG CX,AX
IMUL CX
When CL absolutely, positively, needs to be sign extended before multiplication 
The mul-div codegen path in #DesmetC is sorta a nightmare because so much is reused between multiplication, division, and mod, and because there are some dodgy special-cases in here from 1990 that demonstrably do the wrong thing. Proceeding slowly with machete and torch, laying down test cases as I go.
Heh, well, can't imagine why the assembler doesn't like that instruction.
![MOV DI, WORD 🎵«z_[+18186]](https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/115/932/107/960/489/629/original/e9dfde600e2dc234.png)