/Compiler

From-scratch C compiler for my custom 16-bit CPU

Primary LanguageC

Compiler

A minimal C compiler for my custom 16-bit RISC architecture, capable of compiling itself.

Currently does two passes:

  1. Parse to AST (also analyzes variable lifetime)
  2. Generate Code from AST (no IR, fprintf straight to output file)

Example

Source Assembly 
struct coord
{
    int x;
    int y;
};

int foo (int n, struct coord* coords)
{
    int sum = 0;
    for (int i = 0; i < n; i++)
        sum += coords[i].x * coords[i].y;

    return sum;
}
 
_foo:
mov r0, 0
mov r1, 0
for_loop0:
sub rz, r1, [sp-2]
jmp_ns for_break0
mul r2, r1, 2
add r2, [sp-3]
mul r3, r1, 2
add r3, [sp-3]
add r3, 1
mov r5, [r3]
mul r4, [r2], r5
add r0, r4
for_continue0:
add r1, 1
jmp for_loop0
for_break0:
mov [sp-2], r0
sub sp, 1
mov ip, [sp]

Limitations

This is not a conformant C compiler (at all!). Here are the most important things that are missing or different

  • Type conversion behaviour is different
  • Parsing is not quite the same as in standard C
  • Preprocessor only supports #include, #define, #ifdef, and #pragma once
  • Primitives are:
    • int (alias int16, int16_t)
    • uint (alias uint16, uint16_t, size_t, char)
    • int32 (alias int32_t)
    • uint32 (alias uint32_t)
    • fixed (8.8 fixed point)

These are just off the top of my head, there surely are many others!

Building

Just a CMake project, so

> mkdir bin
> cd bin
> cmake ..

followed by

> cmake --build .

Usage

There are no command-line switches as of now, so just

> ./comp [SOURCE FILES..]

This will generate assembly in out.s and data in data.bin.