[llvm] r183532 - R600: Fix a potential iterator invalidation issue.

[Vincent Lejeune]

Hi,

I initially wrote the code almost like this way, using std::find instead of
std::remove (because there is at most one element that is equal to chan in UpdatedUndef) but
I got memory corruption error in some llvm IR.

Vincent

----- Mail original -----
> De : Benjamin Kramer <benny.kra at googlemail.com>
> À : llvm-commits at cs.uiuc.edu
> Cc : 
> Envoyé le : Vendredi 7 juin 2013 18h13
> Objet : [llvm] r183532 - R600: Fix a potential iterator invalidation issue.
> 
> Author: d0k
> Date: Fri Jun  7 11:13:49 2013
> New Revision: 183532
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=183532&view=rev
> Log:
> R600: Fix a potential iterator invalidation issue.
> 
> As a bonus this reduces the loop from O(n^2) to O(n).
> 
> Modified:
>     llvm/trunk/lib/Target/R600/R600OptimizeVectorRegisters.cpp
> 
> Modified: llvm/trunk/lib/Target/R600/R600OptimizeVectorRegisters.cpp
> URL: 
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/R600/R600OptimizeVectorRegisters.cpp?rev=183532&r1=183531&r2=183532&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/R600/R600OptimizeVectorRegisters.cpp (original)
> +++ llvm/trunk/lib/Target/R600/R600OptimizeVectorRegisters.cpp Fri Jun  7 
> 11:13:49 2013
> @@ -198,11 +198,9 @@ MachineInstr *R600VectorRegMerger::Rebui
>          .addReg(SubReg)
>          .addImm(Chan);
>      UpdatedRegToChan[SubReg] = Chan;
> -    for (std::vector<unsigned>::iterator RemoveIt = UpdatedUndef.begin(),
> -        RemoveE = UpdatedUndef.end(); RemoveIt != RemoveE; ++ RemoveIt) {
> -      if (*RemoveIt == Chan)
> -        UpdatedUndef.erase(RemoveIt);
> -    }
> +    UpdatedUndef.erase(
> +        std::remove(UpdatedUndef.begin(), UpdatedUndef.end(), Chan),
> +        UpdatedUndef.end());
>      DEBUG(dbgs() << "    ->"; Tmp->dump(););
>      (void)Tmp;
>      SrcVec = DstReg;
> 
> 
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