General Category > Implementation Details

Why do we need Clang and LLVM?

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lerno:
LLVM and Clang are huge codebases that takes forever to compile whenever you want to play around with C2. That is bad.
LLVM offers excellent optimizations. That is good.

Here is an idea:

- For debug builds, initially use TinyCC (Tiny C Compiler)
- For optimized builds, use LLVM / Clang (and possibly later LLVM IR directly)

TinyCC is... tiny compared to LLVM. It's also very, very fast. TinyCC is also built to be fed C code directly.

lerno:
On my older laptop LLVM compilation takes about 12 hours. When trying the c2-docker version, it died halfway through due to lack of virtual memory. After running a few hours. LLVM is a resource hog.

bas:
(see other post about LLVM/Clang).

In the beginning I was hoping on being able to reuse Clang's AST. That was not the case. Still
just using the Tokenizer and Diagnostics engine already saved a lot of time. Additionally most of
C2's parsing is heavily based on/inspired by Clang's parser.

lerno:
My experience is that lexing is actually the most straightforward part of writing a parser?

lerno:
One thing would be to localize the DiagnosticsEngine to part of the code and call it through a wrapper. That way it's straightforward to replace it.

Can you explain what you use Clang's preprocessing for? Are we parsing any of standard C so that we need it as input?

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