[LLVMdev] MachineBasicBlock insertion and use/def list update

[Bin Zeng]

  Hi all,

I am still stumped on the same bug. Did anyone try to insert 
MachineBasicBlock into a MachineFunction?
Any advice will be appreciated. Thanks a lot in advance.

~Bin
----------------------------------------------------------------------------------------------------------------------------
Thanks a lot Jeff.  I changed the setNumber function call to
MBB->setNumber(mf->addToMBBNumbering(MBB)); But it still enters the 
infinite loop.
It is strange that if I insert all these instructions into an existing 
MachineBasicBlock, the
error disappears.  It is due to the way I create or insert 
MachineBasicBlocks in a wrong way.
When each operand is added to an instruction, the use/def list for the 
function will be updated.
It should not happen that an MachineOperand.Contents.Reg.Next points to 
itself.

Anyway, thanks a lot again for your reply.

~Bin

On 10/20/2010 3:53 PM, Jeff Kunkel wrote:
>  From what I gathered about MachineBasicBlocks are the blocks have to
> be added in a certain way. One cannot just choose any number, because
> the MachineFunction basically owns a basic block. So the call (1) will
> add the number to the block and add the block to the function. The
> final mf.insert(mbb) will place where the block will be inserted
> relative to other blocks, but the numbering is not in ascending
> ordering.
>
> (1) mbb->setNumber( mf->addToMBBNumbering( mbb ) );
>
> My 2 cents,
> Jeff Kunkel
>
> On Wed, Oct 20, 2010 at 1:52 PM, Bin Zeng<ezengbin at gmail.com>  wrote:
>>   Hi all,
>>
>> I am really stumped on a problem for long. I could not figure out why.
>> That is why i am here. OK, here is the problem:
>> I tried to insert a MachineBasicBlock into a function. Here is the code
>> snippet:
>>
>> // insert a machine basic block with the error_label into MF and 
>> before I
>> // Pred is the predecessor of the block to be inserted
>> // the new basic block is inserted right before I
>> void X86CFIOptPass::insertBasicBlockBefore(MachineFunction&MF,
>>                         MachineBasicBlock *Pred,
>>                         MachineFunction::iterator I){
>>    const BasicBlock* LLVM_BB = Pred->getBasicBlock();
>>    MachineBasicBlock * MBB = MF.CreateMachineBasicBlock(LLVM_BB); //
>> create a MBB
>>    MBB->setNumber(19880616); // set the number of MBB to be 19880616
>> which is used as an ID
>>
>>    Pred->addSuccessor(MBB);
>>    const TargetInstrInfo *TII = MF.getTarget().getInstrInfo();
>>    DebugLoc dl;
>>    // CALLpcrel32 abort
>>    BuildMI(MBB,dl,TII->get(X86::CALLpcrel32)).addExternalSymbol("abort");
>>    // JNE_4 error_label
>>    BuildMI(MBB,dl,TII->get(X86::JNE_4)).addExternalSymbol("error_label");
>>    // MOV32ri %eax, 0
>>    BuildMI(MBB,dl,TII->get(X86::MOV32ri),X86::EAX).addImm(0);
>>    // CALL32r %eax
>>    // BuildMI(MBB,dl,TII->get(X86::CALL32r)).addReg(X86::EAX);
>>    MF.insert(I,MBB);
>> }
>>
>> When I tried to dump the code after the insertion, the program enters an
>> infinite loop
>> in the while loop inside MachineRegisterInfo.h:defusechain_iterator
>> &operator++().
>> Basically, the CALLpcrel32 instruction has a register operand that
>> points to itself, that is,
>> Contents.Reg.Next stores the address of itself. Does anyone knows how to
>> insert a MachineBasicBlock
>> into a function? Any advice will be appreciated. Thanks in advance.
>>
>> ~Bin
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