[llvm-commits] [llvm] r101930 - /llvm/trunk/lib/CodeGen/MachineLICM.cpp

[Evan Cheng]

On Apr 20, 2010, at 11:45 AM, Jakob Stoklund Olesen wrote:

> Author: stoklund
> Date: Tue Apr 20 13:45:47 2010
> New Revision: 101930
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=101930&view=rev
> Log:
> When MachineLICM is hoisting a physical register after regalloc, make sure the
> register is not killed in the loop.
> 
> This fixes 188.ammp on ARM where the post-ra scheduler would grab a register
> that looked available but wasn't.
> 
> A testcase would be huge and fragile, sorry.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/MachineLICM.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/MachineLICM.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineLICM.cpp?rev=101930&r1=101929&r2=101930&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/MachineLICM.cpp (original)
> +++ llvm/trunk/lib/CodeGen/MachineLICM.cpp Tue Apr 20 13:45:47 2010
> @@ -411,12 +411,25 @@
>   delete[] PhysRegDefs;
> }
> 
> -/// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the
> -/// current loop.
> +/// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the current
> +/// loop, and make sure it is not killed by any instructions in the loop.
> void MachineLICM::AddToLiveIns(unsigned Reg) {
>   const std::vector<MachineBasicBlock*> Blocks = CurLoop->getBlocks();
> -  for (unsigned i = 0, e = Blocks.size(); i != e; ++i)
> -    Blocks[i]->addLiveIn(Reg);
> +  for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
> +    MachineBasicBlock *BB = Blocks[i];
> +    if (!BB->isLiveIn(Reg))
> +      BB->addLiveIn(Reg);
> +    for (MachineBasicBlock::iterator
> +           MII = BB->begin(), E = BB->end(); MII != E; ++MII) {
> +      MachineInstr *MI = &*MII;
> +      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
> +        MachineOperand &MO = MI->getOperand(i);
> +        if (!MO.isReg() || !MO.getReg() || MO.isDef()) continue;
> +        if (MO.getReg() == Reg || TRI->isSuperRegister(Reg, MO.getReg()))

Thanks.

Shouldn't this checks for alias rather than super register? It's bad if any part of the loop invariant is modified.

Evan

> +          MO.setIsKill(false);
> +      }
> +    }
> +  }
> }
> 
> /// HoistPostRA - When an instruction is found to only use loop invariant
> 
> 
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits