[LLVMdev] Steps to addDestination

[Tim Northover]

Hi Rasha,

> for(rit=Result.begin();rit!=Result.end();++rit)
>   {
>           Value* Address= BlockAddress::get (*rit);
>
>            IndirectBrInst *IBI = IndirectBrInst::Create(Address, Result.size(),i->getTerminator() );
>            IBI->addDestination((*rit));
>   }

This would be creating a block looking something like:
    [ Do stuff ]
    indirectbr i8* blockaddress(@foo, %result1), [label %result1]
    indirectbr i8* blockaddress(@foo, %result2), [label %result2]
    [...]
    indirectbr i8* blockaddress(@foo, %resultN), [label %resultN]

which isn't valid LLVM IR. Each basic block has to have a single
branch at the end so you need to create the IndirectBrInst outside the
loop.

How do you decide which of the results you want to jump to at
run-time? I think that's the key question you have to answer. You want
to emit LLVM IR to make this decision and produce a single Value
representing it, then use the value just once to create a single
indirectbr.

Your code might look like:
    Value *Address = emitCodeToChooseResult(Results, Loc);

    IndirectBrInst *IBI = IndirectBrInst::Create(Address, Result.size(), i);
    for (rit = Result.begin(); rit != Result.end(); ++rit)
      IBI->addDestination(*rit);

Cheers.

Tim.