[LLVMdev] Your question about LLVM
mclagett at hotmail.com
Fri Oct 7 07:42:39 PDT 2011
Wondering if you've gotten any further answering the question you pose below?
I also am interested in being able to generate a JVM backend, but not departing, as you are, from coding in java itself, but rather as a means to integrate my own custom vm with Java and be able to produce and consume java code easily from my custom environment.
Just curios if you made any progress answering this question for yourself and the final one you pose: "Is LLVM for me?"
Sorry if I'm repeating something that was already said.
I was just thinking "why the heck do I seem headed for JVM generation if
what I want to use is LLVM", and this is the result:
I'm coming from a Java background. I'm using Eclipse, I'm used to the
syntax highlighting, cross referencing and refactoring support that
I know I will want to have the same infrastructure for my language, and
I want it written in my language. I WILL need a JVM backend, no matter what.
Now, I'd still love to use LLVM. It has a lot to offer for the phases
"above" code generation. I don't need register allocation, but I'd like
to make use of common constant elimination, loop unrolling, inlining, or
the pass management infrastructure; that's a whole lot of code I don't
need to write.
And when it comes to generating raw machine code, I can confidently say:
develop in Eclipse and run the stuff as JVM code, but deploy using the
machine-code backend provided by LLVM.
So my conclusion is:
To make LLVM attractive for us Java-based language designers, we need
the means to write a JVM backend.
The actual backend is easy, libraries for class file and JAR generation
I'd need help for:
* Determining where exactly the line is drawn between "this LLVM
component is useful for JVM bytecode generation" and "this LLVM
component isnt". (Constant folding would be, register allocation would
not, but there's a lot of gray areas between these two.)
* Not being a JNI or C++ expert, building the JNI infrastructure that
would allow calling LLVM components from Java.
* Not being a true Eclipse expert, wrapping LLVM binaries as Eclipse
plugins. Eclipse expects plugins to be available for download via HTTP,
with some XML that describes dependencies. Setting this up would be
easy, getting the details right would be work.
That's just my specific skillset, other language designers might have
different ones, but I guess it is not very likely that the exact right
combination will come up easily. There aren't many people around who're
experts in C++, Java, and Eclipse.
Oh, and the question I'm having is: Is LLVM for me?
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