[llvm-commits] [llvm] r65123 - /llvm/trunk/lib/Transforms/Utils/Mem2Reg.cpp

[Chris Lattner]

On Feb 20, 2009, at 8:31 AM, Zhou Sheng wrote:

> Author: sheng
> Date: Fri Feb 20 10:31:35 2009
> New Revision: 65123
>
> URL: http://llvm.org/viewvc/llvm-project?rev=65123&view=rev
> Log:
> patch to update the line number information in pass -mem2reg.
> Currently this pass will delete the variable declaration info,
> and keep the line number info. But the kept line number info is not  
> updated,
> and some is redundant or not correct, this patch just updates those  
> info.

Hi Sheng,

High level question: why do you want mem2reg to do this?  Doesn't  
instcombine already do it?  If not, it should.

> +/// Remove the invalid or redundant debug information.
> +static void CleanDbgInfo(Function& F) {
> +  std::vector<Instruction*> DeadDbgs;
> +  for (Function::iterator BBI = F.begin(), BBE = F.end(); BBI !=  
> BBE; ++BBI) {
> +    if (BBI->size() <= 1)
> +      continue;

size() is O(n), please don't call it here.

>
> +    for (BasicBlock::iterator I = BBI->begin(), E = BBI- 
> >getTerminator();
> +         I != E; ++I) {
> +      BasicBlock::iterator NextI = I;
> +      ++NextI;
> +      if (isa<DbgStopPointInst>(I) && isa<DbgStopPointInst>(NextI))
> +        DeadDbgs.push_back(I);

You don't need the temporary vector, just preincrement the iterator.

>
> +      else if (isa<DbgStopPointInst>(I) && isa<BranchInst>(NextI))
> +        DeadDbgs.push_back(I);
> +    }

Deleting stoppoints before branches isn't correct.  You can have  
control flow within a line (e.g. ?: expressions) and the intermediate  
blocks need to get that stoppoint.

-Chris