[llvm-commits] [llvm] r82629 - /llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp

[David Goodwin]

Because then the superreg is never killed... I think that will cause  
an assertion in the following code when the superreg is defined again.

David

On Sep 23, 2009, at 10:34 PM, Evan Cheng wrote:

>
> On Sep 23, 2009, at 9:35 AM, David Goodwin wrote:
>
>> Author: david_goodwin
>> Date: Wed Sep 23 11:35:25 2009
>> New Revision: 82629
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=82629&view=rev
>> Log:
>> Fix bug in kill flag updating for post-register-allocation  
>> scheduling. When the kill flag of a superreg needs to be cleared  
>> because there are one or more subregs live, we instead add implicit- 
>> defs of those subregs and leave the kill flag on the superreg. This  
>> allows us to end the live-range of the superreg without ending the  
>> live-ranges of the subregs.
>>
>
> Hmm. This seems wrong. You have changed the code so the live  
> registers are defined by implicit_def's. Why not remove the kill of  
> the superreg and add kills of the sub-registers that are no longer  
> used?
>
> Evan
>
>
>> Modified:
>>   llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp?rev=82629&r1=82628&r2=82629&view=diff
>>
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> =====================================================================
>> --- llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/PostRASchedulerList.cpp Wed Sep 23  
>> 11:35:25 2009
>> @@ -178,6 +178,11 @@
>>                                      unsigned LastNewReg,
>>                                      const TargetRegisterClass *);
>>    void StartBlockForKills(MachineBasicBlock *BB);
>> +
>> +    // ToggleKillFlag - Toggle a register operand kill flag. Other
>> +    // adjustments may be made to the instruction if necessary.  
>> Return
>> +    // true if the operand has been deleted, false if not.
>> +    bool ToggleKillFlag(MachineInstr *MI, MachineOperand &MO);
>>  };
>> }
>>
>> @@ -822,6 +827,40 @@
>>  }
>> }
>>
>> +bool SchedulePostRATDList::ToggleKillFlag(MachineInstr *MI,
>> +                                          MachineOperand &MO) {
>> +  // Setting kill flag...
>> +  if (!MO.isKill()) {
>> +    MO.setIsKill(true);
>> +    return false;
>> +  }
>> +
>> +  // If MO itself is live, clear the kill flag...
>> +  if (KillIndices[MO.getReg()] != ~0u) {
>> +    MO.setIsKill(false);
>> +    return false;
>> +  }
>> +
>> +  // If any subreg of MO is live, then create an imp-def for that
>> +  // subreg and keep MO marked as killed.
>> +  bool AllDead = true;
>> +  const unsigned SuperReg = MO.getReg();
>> +  for (const unsigned *Subreg = TRI->getSubRegisters(SuperReg);
>> +       *Subreg; ++Subreg) {
>> +    if (KillIndices[*Subreg] != ~0u) {
>> +      MI->addOperand(MachineOperand::CreateReg(*Subreg,
>> +                                               true  /*IsDef*/,
>> +                                               true  /*IsImp*/,
>> +                                               false /*IsKill*/,
>> +                                               false /*IsDead*/));
>> +      AllDead = false;
>> +    }
>> +  }
>> +
>> +  MO.setIsKill(AllDead);
>> +  return false;
>> +}
>> +
>> /// FixupKills - Fix the register kill flags, they may have been made
>> /// incorrect by instruction reordering.
>> ///
>> @@ -860,9 +899,9 @@
>>      }
>>    }
>>
>> -    // Examine all used registers and set kill flag. When a register
>> -    // is used multiple times we only set the kill flag on the first
>> -    // use.
>> +    // Examine all used registers and set/clear kill flag. When a
>> +    // register is used multiple times we only set the kill flag on
>> +    // the first use.
>>    killedRegs.clear();
>>    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
>>      MachineOperand &MO = MI->getOperand(i);
>> @@ -889,8 +928,12 @@
>>      }
>>
>>      if (MO.isKill() != kill) {
>> -        MO.setIsKill(kill);
>> -        DEBUG(errs() << "Fixed " << MO << " in ");
>> +        bool removed = ToggleKillFlag(MI, MO);
>> +        if (removed) {
>> +          DEBUG(errs() << "Fixed <removed> in ");
>> +        } else {
>> +          DEBUG(errs() << "Fixed " << MO << " in ");
>> +        }
>>        DEBUG(MI->dump());
>>      }
>>
>>
>>
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