[llvm-commits] [llvm] r107847 - in /llvm/trunk: include/llvm/CodeGen/RegisterScavenging.h lib/CodeGen/PrologEpilogInserter.cpp lib/CodeGen/RegisterScavenging.cpp

[Jakob Stoklund Olesen]

On Jul 7, 2010, at 5:38 PM, Jim Grosbach wrote:
> Modified: llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp?rev=107847&r1=107846&r2=107847&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp (original)
> +++ llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp Wed Jul  7 19:38:54 2010
> @@ -885,10 +885,20 @@
>             // Scavenge a new scratch register
>             CurrentVirtReg = Reg;
>             const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
> -            CurrentScratchReg = RS->FindUnusedReg(RC);
> -            if (CurrentScratchReg == 0)
> +            const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
> +            BitVector Candidates(TRI->getNumRegs());
> +            RS->getRegsAvailable(RC, Candidates);
> +
> +            // If there are any registers available, use the one that's
> +            // unused for the longest after this instruction. That increases
> +            // the ability to reuse the value.
> +            if (Candidates.any()) {
> +              MachineBasicBlock::iterator UMI;
> +              CurrentScratchReg = RS->findSurvivorReg(I, Candidates, 25, UMI);
> +            } else {
>               // No register is "free". Scavenge a register.
>               CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
> +            }
> 
>             PrevValue = Value;
>           }

This looks like a method that escaped from RegScavenger. Isn't RegScavenger::scavengeRegister already doing this?

I think

               CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);

is all you need.


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