[LLVMdev] Manipulating basic blocks with the C bindings

[Kenneth Uildriks]

On Thu, May 27, 2010 at 5:47 PM, Evan Shaw <chickencha at gmail.com> wrote:
> I'm writing a frontend with the LLVM C bindings for a language that
> has a goto statement, similar to C's. I'm having some trouble figuring
> out what to do for the case where the label is declared after the
> goto, like this:
>
> goto label;
> ...
> label:
> ...
>
> When I generate the code for the goto, I'd like to create a basic
> block that's not inserted anywhere in particular and then put it in
> the right place when I hit the label (or error out appropriately if I
> never find it). It looks like the C++ API allows one to do what I'm
> describing, but I don't see a way to do it with the C bindings.\

When you hit the "goto", create an empty basic block with
LLVMAppendBasicBlockInContext and put in an unconditional branch to
it.  Later, when you hit the label, put another unconditional branch
to that same block, then call LLVMPositionBuilderAtEnd(labelBlock) and
continue on your way.


>
> I'd like to add the following functions. Hopefully my intent is clear.
> I'm very open to name suggestions, as these are a mouthful:
>
> void LLVMAppendExistingBasicBlockInContext(LLVMContextRef C,
> LLVMValueRef Fn, LLVMBasicBlock BB);
> void LLVMInsertExistingBasicBlockInContext(LLVMContextRef C,
> LLVMBasicBlockRef InsertBeforeBB, LLVMBasicBlock BB);
> void LLVMAppendExistingBasicBlock(LLVMValueRef Fn, LLVMBasicBlock BB);
> void LLVMInsertExistingBasicBlock(LLVMBasicBlockRef InsertBeforeBB,
> LLVMBasicBlock BB);
>
> Does this sound reasonable? Am I missing something?
>
> - Evan
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>