Merry Christmas 🎄

At about 1 am christmas morning, I "finished" credence.

Five months. If you subtract the hours of my work organization, you can see exactly when I started on the backend in my GitHub contribution graph:

Credence has been the culmination of a lot of professional and hobby work since the idea was first conceived. The first commit in the parser is about 7 years old. Since then, I've designed languages and built compilers at my workplace.

It is my Magnum Opus

As of last night, I am wholly content with the machine code it generates for x64 on Linux, and BSD. I will leave ARM64 as a separate, future project.

The final test was the translation of switch control structures from my IR, the JMP_E ITA statement.

If you're interested in what the machine code looks like, you should peek at the test suite. The code coverage is impressively exhaustive, with about 80% of all functions and lines covered, according to llvm-lcov.

As I begin to reflect, by far the most challenging section was designing the Intermediate Representation. Unlike other parts, its design was purely academic - there is no specification to follow. The last time I was in this position was when I needed to re-create left-recursion in a PEG grammar for work, for which I needed a Microsoft paper to complete.

I am very thankful for this lecture at Stanford - it gave me a lot of inspiration. Here is a snippet of the IR for the switch program above:

__main():
 BeginFunc ;
    LOCL x;
    LOCL y;
    x = (10:int:4);
_L2:
    _t5 = x >= (5:int:4);
    IF _t5 GOTO _L4;
_L3:
    y = (10:int:4);
_L1:
    LEAVE;
_L4:
    _t6 = CMP x;
    JMP_E _t6 (10:int:4) _L8;
    JMP_E _t6 (6:int:4) _L16;
    JMP_E _t6 (7:int:4) _L18;

...
...
...

_L18:
    x = (5:int:4);
    GOTO _L17;
 EndFunc ;

I have learned that regardless of the size of your compiler or interpreter, you should choose a good IR for your project's size. It makes the difference.

I am going to take a break and spend some time in the mountains. Next time around, I want to work on something much closer to hardware - I was thinking an audio interface and its drivers.

Until then 🤘