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Comment by chongli | Hacker News Reader

It's not really more/less features so much as it is a tradeoff. LLVM is extremely powerful in that it lets you write front-ends for many different languages without worrying about the complexities of native code gen. Likewise, it lets you write backends for other target platforms (i.e. JavaScript), allowing you to gain the ability to port those languages to new platforms easily. Thirdly, you can write optimizers for LLVM's intermediate representation and gain the benefit across most/all front-end languages and back-end platforms.

GCC, on the other hand, seems to have a much narrower focus but with a lot more optimizations and weird extensions.

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This is exactly GCC's architecture as well, where front-ends are transpiled into a generic language, which is then compiled into native code for a given platform.

That's how GCC works internally, but neither the front-ends nor the back-ends are available to use individually. Indeed, RMS specifically avoided having a flexible architecture similar to llvm, because he was afraid such flexibility would be used for non-GPL "plugins".

If you can dump or generate the IR you can use the front or back ends as you please, no? You might have to write something that reads in the IR.

Thats a lot of work for what you get out of the box with clang. There is a whole community of tooling around llvm for these types of use case, so why use gcc?

Sure, I was just arguing possibility, not feasibility.

GCC supports external dynamically loaded plugins since 4.5.0 (3 years ago)

http://gcc.gnu.org/onlinedocs/gccint/Plugins.html

The wiki has links to some plugins too http://gcc.gnu.org/wiki/plugins

Sure, but what about the inverse? With LLVM you can use frontends as libraries for integrating into an (possibly non-free) IDE for completion, syntax highlighting, refactoring etc. This is especially powerful because you can avoid serialization and just keep the ASTs in memory. I'm not aware of this being possible with GCC, but I could be wrong.

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