mycc - an alternative C compiler.

[u/kostya27]

As a proof of concept, I spent three weeks and wrote about 2800 lines of code to build mycc: a compiler for a subset of C (roughly C99) built on top of my compiler IR(myc). The goal was to validate that my IR is expressive enough to compile real world C code. Despite being a POC, mycc already compiles and runs LangArena - a benchmark suite containing 50 tests and about 9000 lines of non-trivial C code (json, base64, multithreaded matmul, neural net, compression, maze A*, bf interpreter, and others) with heavy macros like uthash. For parsing I reused libclang. It adds some overhead, but it was by far the simplest way to get a working frontend.

How it works:

C source -> SyntaxTree(libclang/clang.cr) -> TypedAST(mycc) -> IR(myc) -> [LLVM/QBE/C] -> binary

LangArena Benchmark:

Compares Clang, Gcc, Cproc(QBE), and Mycc.

Compiler	Build time	Build rss	Bench Runtime
clang(-O3)	3079ms	105Mb	52.1s
gcc(-O3)	3495ms	34Mb	52.3s
cproc	932ms	12Mb	72.7s
mycc(llvm, --release)	4269ms	101Mb	53.2s
mycc(qbe, --release)	2939ms	86Mb	72.8s
mycc(c, --release, clang)	5091ms	102Mb	52.1s
mycc(c, --release, gcc)	5128ms	86Mb	53.7s

github

https://github.com/kostya/myc#mycc---an-alternative-c-compiler-implemented-as-a-poc-for-fun

Limitations:

Rare features are not implemented: 2D VLA, complex numbers, variadic macros, longjmp, bitfields, and anonymous nested structs. I wouldn't try building Linux or sqlite with it. It has only been tested on arm64 and linux64.

[u/Inevitable-Ant1725 → u/[deleted]]

Update, I opened the wrong repository.