[LLVMdev] Erasing Instruction

[John Criswell]

Chayan Sarkar wrote:
> Hi,
>
> Can anyone tell me how to erase an instruction, (specially a
> load/store instruction) ?
>
> If I use Instr->eraseFromParent(), I get following error. Note the
> instruction does not have any use.
>   

Are you calling the eraseFromParent() method on an Instruction inside a 
loop?  If so, is that loop iterating over instructions using an iterator?

If so, then the problem might be that you're invalidating the iterator 
that iterates over instructions.  When I delete instructions, I 
typically iterate over the list of instructions and record those I want 
to delete into a std::vector<> and then use another loop that fetches 
the last element in the std::vector<> and deletes it.  While less 
efficient, I never have iterator invalidation errors.

-- John T.

>
> opt: /home/chayan/llvm/llvm-2.6/include/llvm/ADT/ilist.h:218:
> llvm::ilist_iterator<NodeTy>&
> llvm::ilist_iterator<NodeTy>::operator++() [with NodeTy =
> llvm::Instruction]: Assertion `NodePtr && "++'d off the end of an
> ilist!"' failed.
> 0   opt 0x084560a8
> Stack dump:
> 0.	Running pass 'Function Pass Manager' on module '<stdin>'.
> 1.	Running pass 'Testing try-outs' on function '@test'
> ./unoptrun.sh: line 10: 32064 Aborted                 opt -load
> /home/chayan/llvm/llvm-2.6/Release/lib/test.so -test < input.bc >
> output.bc
> llvm-dis: Invalid bitcode signature
>
>
> Any idea how to solve this.
>
> Regards,
> Chayan
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