[LLVMdev] Basic block liveouts

[Jeff Kunkel]

Because I feel bad for giving a non-answer:

An easy way to find if a virtual register is alive after the basic block is
to
While iterating over the virtual registers
- Check to see if the virtual register's "next" value exists outside of the
basic block.

for instance:

std::vector<unsigned> findLiveOut( MachineBasicBlock * mbb ) {
  std::vector<unsigned> liveout;
  for( MachineBasicBlock::iterator mbbi = mbb->begin(), mbbe = mbb->end();
mbbi != mbbe; ++mbbi ) {
    for( opi = 0, ope = mbbi->getNumOperands(); opi < ope; ++opi ) {
      MachineOperand & operand = mbbi->getOperand(opi);
      if( operand.isReg() == false )
        continue;
      if( operand.getReg() == 0 )
        continue;
      if( ! TargetRegisterInfo::isVirtualRegister(operand.getReg()) )
        continue;
      if( mbb != operand.getNextOperandForReg()->getParent()->getParent() )
        liveout.push_back( operand.getReg() );
    }
  }
  return liveout;
}


On Fri, Nov 5, 2010 at 7:41 AM, s Last namerc <srcsrc84 at yahoo.com> wrote:

> Is there an easy way to obtain all liveout variables of a basic block?
> Liveins
> can be found for each MachineBasicBlock, but I can only find liveouts for
> the
> whole function, at MachineRegisterInfo. Do I need to find them out
> manually?
>
>
>
>
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