llvm dev - Oct 2017 - How to use SplitBlockAndInsertIfThen() correctly?

The way I have used SplitBlockAndInsertIfThen() throws this assertion
error: "Assertion `IDomNode && "Not immediate dominator
specified for
block!"' failed". Consider the following abstraction:

======================I1
I2
======================What I am trying to achieve is:
======================I1
I_cond
    I_then1
    I_then2
I_new1
I_new2
I2
======================
In plain English
   - Split the block between I1 and I2
   - Insert an ICMP at the end of first block
   - Add a couple of instructions (I_then1, I_then2) to the THEN block
   - Add a couple of instruction at the beginning of the last block
preceding I2 (I_new1, I_new2)


My code roughly looks like:

======================        Instruction *I2 = I1->getNextNode();     //
Next instruction
        TerminatorInst *then_inst;

        if(condition) {
            Value *I_cond = builder.CreateICmpNE(_, _);

            // Split the basic block
            then_inst = SplitBlockAndInsertIfThen(I_cond, I2, false);

            // Set the insert point before terminator of THEN block
            builder.SetInsertPoint(then_inst);

            // Add new instructions
            I_then1
            I_then2
        }

        // Set the insert point before the next instruction
        builder.SetInsertPoint(I2);

       // Add new instructions
        I_new1
        I_new2

======================
What's wrong with my approach? How to fix it?

-- 

Thanks & Regards,
Dipanjan
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I believe the problem comes from inserting instructions both at the THEN
block and the beginning of the tail block. Any idea how's that possible?

On 21 October 2017 at 01:59, Dipanjan Das <mail.dipanjan.das at gmail.com>
wrote:
>
> The way I have used SplitBlockAndInsertIfThen() throws this assertion
> error: "Assertion `IDomNode && "Not immediate dominator
specified for
> block!"' failed". Consider the following abstraction:
>
> ======================> I1
> I2
> ======================> What I am trying to achieve is:
> ======================> I1
> I_cond
>     I_then1
>     I_then2
> I_new1
> I_new2
> I2
> ======================>
> In plain English
>    - Split the block between I1 and I2
>    - Insert an ICMP at the end of first block
>    - Add a couple of instructions (I_then1, I_then2) to the THEN block
>    - Add a couple of instruction at the beginning of the last block
> preceding I2 (I_new1, I_new2)
>
>
> My code roughly looks like:
>
> ======================>         Instruction *I2 = I1->getNextNode(); 
// Next instruction
>         TerminatorInst *then_inst;
>
>         if(condition) {
>             Value *I_cond = builder.CreateICmpNE(_, _);
>
>             // Split the basic block
>             then_inst = SplitBlockAndInsertIfThen(I_cond, I2, false);
>
>             // Set the insert point before terminator of THEN block
>             builder.SetInsertPoint(then_inst);
>
>             // Add new instructions
>             I_then1
>             I_then2
>         }
>
>         // Set the insert point before the next instruction
>         builder.SetInsertPoint(I2);
>
>        // Add new instructions
>         I_new1
>         I_new2
>
> ======================>
> What's wrong with my approach? How to fix it?
>
> --
>
> Thanks & Regards,
> Dipanjan
>


-- 

Thanks & Regards,
Dipanjan
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