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

[Evan Cheng]

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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