llvm dev - Mar 2020 - How to simply split MachineBasicBlock ?

Hi

I am developing some machine function pass.

I want to split MachineBasicBlcok when I find some specific machine
instruction.

But I don't insert or delete any machine instruction.

I just "simply" , "purely" split the MachineBasicBlcok.

(So, I stole the idea from ARM64BranchRelaxation::splitBlockBeforeInstr.)

This is my code :

// I would pass call instruction to this function

void split_mbb(MachineInstr* mi){
  MachineBasicBlock* mbb=mi->getParent();
  MachineFunction* mf=mbb->getParent();
  MachineBasicBlock*
new_mbb=mf->CreateMachineBasicBlock(mbb->getBasicBlock());

  MachineFunction::iterator mbb_it(mbb);
  mf->insert(mbb_it,new_mbb);
  new_mbb->splice(new_mbb->end(),mbb,mbb->begin(),mi);
}

Originally, mi is in BB.
(mi would be a call instruction)
(do not consider mi is a branch instruction)
BB --> BB1 , BB2
Then, I split BB, mi is the first instruction of BB2.
And the instructions before mi are in BB1.

But now, I use  my machine function pass to compile some test programs.

And these test programs can't execute ,  always segment fault.

Is there any problem in my split_mbb ?

How to "simply" split MachineBasicBlock ?

Thank you !!
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Did you transfer the successors of BB1 to BB2 and add BB2 as a successor of
BB1? This note in code you referenced refers to that "NOTE: Successor list
of the original BB is out of date after this function, and must be updated
by the caller!"

See this code in ARMConstantIslands::splitBlockBeforeInstr

  // Update the CFG.  All succs of OrigBB are now succs of NewBB.
  NewBB->transferSuccessors(OrigBB);

  // OrigBB branches to NewBB.
  OrigBB->addSuccessor(NewBB);



~Craig


On Thu, Mar 12, 2020 at 10:20 PM PenYiWang via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi
>
> I am developing some machine function pass.
>
> I want to split MachineBasicBlcok when I find some specific machine
> instruction.
>
> But I don't insert or delete any machine instruction.
>
> I just "simply" , "purely" split the MachineBasicBlcok.
>
> (So, I stole the idea from ARM64BranchRelaxation::splitBlockBeforeInstr.)
>
> This is my code :
>
> // I would pass call instruction to this function
>
> void split_mbb(MachineInstr* mi){
>   MachineBasicBlock* mbb=mi->getParent();
>   MachineFunction* mf=mbb->getParent();
>   MachineBasicBlock*
> new_mbb=mf->CreateMachineBasicBlock(mbb->getBasicBlock());
>
>   MachineFunction::iterator mbb_it(mbb);
>   mf->insert(mbb_it,new_mbb);
>   new_mbb->splice(new_mbb->end(),mbb,mbb->begin(),mi);
> }
>
> Originally, mi is in BB.
> (mi would be a call instruction)
> (do not consider mi is a branch instruction)
> BB --> BB1 , BB2
> Then, I split BB, mi is the first instruction of BB2.
> And the instructions before mi are in BB1.
>
> But now, I use  my machine function pass to compile some test programs.
>
> And these test programs can't execute ,  always segment fault.
>
> Is there any problem in my split_mbb ?
>
> How to "simply" split MachineBasicBlock ?
>
> Thank you !!
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Thank You !!
Help me a lot !!


Craig Topper <craig.topper at gmail.com> 於 2020年3月13日 週五 下午2:36寫道：
> Did you transfer the successors of BB1 to BB2 and add BB2 as a successor
> of BB1? This note in code you referenced refers to that "NOTE:
Successor
> list of the original BB is out of date after this function, and must be
> updated by the caller!"
>
> See this code in ARMConstantIslands::splitBlockBeforeInstr
>
>   // Update the CFG.  All succs of OrigBB are now succs of NewBB.
>   NewBB->transferSuccessors(OrigBB);
>
>   // OrigBB branches to NewBB.
>   OrigBB->addSuccessor(NewBB);
>
>
>
> ~Craig
>
>
> On Thu, Mar 12, 2020 at 10:20 PM PenYiWang via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi
>>
>> I am developing some machine function pass.
>>
>> I want to split MachineBasicBlcok when I find some specific machine
>> instruction.
>>
>> But I don't insert or delete any machine instruction.
>>
>> I just "simply" , "purely" split the
MachineBasicBlcok.
>>
>> (So, I stole the idea from
ARM64BranchRelaxation::splitBlockBeforeInstr.)
>>
>> This is my code :
>>
>> // I would pass call instruction to this function
>>
>> void split_mbb(MachineInstr* mi){
>>   MachineBasicBlock* mbb=mi->getParent();
>>   MachineFunction* mf=mbb->getParent();
>>   MachineBasicBlock*
>> new_mbb=mf->CreateMachineBasicBlock(mbb->getBasicBlock());
>>
>>   MachineFunction::iterator mbb_it(mbb);
>>   mf->insert(mbb_it,new_mbb);
>>   new_mbb->splice(new_mbb->end(),mbb,mbb->begin(),mi);
>> }
>>
>> Originally, mi is in BB.
>> (mi would be a call instruction)
>> (do not consider mi is a branch instruction)
>> BB --> BB1 , BB2
>> Then, I split BB, mi is the first instruction of BB2.
>> And the instructions before mi are in BB1.
>>
>> But now, I use  my machine function pass to compile some test programs.
>>
>> And these test programs can't execute ,  always segment fault.
>>
>> Is there any problem in my split_mbb ?
>>
>> How to "simply" split MachineBasicBlock ?
>>
>> Thank you !!
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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