[LLVMdev] simple questions -and wiki

[Chris Lattner]

On Tue, 24 Apr 2007, Basile STARYNKEVITCH wrote:
> Some people thought about a n LLVM wiki. Is there some alreadly? I wish it
> would be linked from LLVM.org site.

It is wiki.llvm.org, but it is only partially set up. For now, please send 
email to John Criswell if you want write access.

> Here are a few questions which I would like to be answered (preferably 
> on a Wiki, to possibly participate):
>
> assuming that LLVM (latest from CVS) was configure-d with
>  ./configure '--ENABLE-TARGETS=HOST-ONLY' '--WITH-GNU-LD'
>
> My main (currently platonic - ie no real work yet) interest is in dynamic
> code generation within my application. but i might want possibly to persist
> the generated code (and somehow relead it at next application run).
>
> how to emit an llvm moduls as (all of)
>  an elf shared object
>  a generated c file
>  a JIT-ted in-memory module
>
> are all the above compatible?

These can all be generated with llc or lli.

> does an elf reader exists which does a dlopen (or very near equivalent)?

Why not just use dlopen?

> if the generated c file is compiled (with e.g. -fpic -shared on amd64/linux)
> does the so compiled .so file is equivalent to the elf shared object (are
> the symbols the same)?

Yes.

> and to the JIT-ed memory module?

I don't know what this means.

> are machine code quality of JIT-ed memory module or of elf shared object
> comparable?

Yes, they use the same code generator.

> i'm also suggessting adapting the simple JIT examples (or providing new
> ones) to possibly emit c file or elf shared object?

Why would you want to emit C?

> how to delete the code in a JIT-ed in-memory module?

ExecutionEngine::freeMachineCodeForFunction

> i cannot figure out how to canonically get the host target (ie the
> TargetMachine argument to ElfWriter) when configured with
> '--enable-targets=host-only' - shouldn't we have only one TargetMachine in
> that case? Mayvbe a static TargetMachine* TargetMachine::getHostTarget()
> function could help?

The elf writer isn't stable/complete yet.  I suggest emitting .s files and 
invoking the system assembler.

-Chris

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