[llvm] r182062 - Generate debug info for by-value struct args even if they are not used.

[Bob Wilson]

On May 16, 2013, at 4:44 PM, Adrian Prantl <aprantl at apple.com> wrote:

> Author: adrian
> Date: Thu May 16 18:44:12 2013
> New Revision: 182062
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=182062&view=rev
> Log:
> Generate debug info for by-value struct args even if they are not used.
> radar://problem/13865940
> 
> Added:
>    llvm/trunk/test/DebugInfo/X86/byvalstruct.ll
> Modified:
>    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=182062&r1=182061&r2=182062&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu May 16 18:44:12 2013
> @@ -6753,9 +6753,15 @@ void SelectionDAGISel::LowerArguments(co
> 
>     // If this argument is unused then remember its value. It is used to generate
>     // debugging information.
> -    if (I->use_empty() && NumValues)
> +    if (I->use_empty() && NumValues) {
>       SDB->setUnusedArgValue(I, InVals[i]);
> 
> +      // Also remember any frame index for use in FastISel.
> +      if (FrameIndexSDNode *FI =
> +          dyn_cast<FrameIndexSDNode>(InVals[i].getNode()))
> +        FuncInfo->setArgumentFrameIndex(I, FI->getIndex());
> +    }

dyn_cast may return 0 if the type does not match, yet you're unconditionally dereferencing the result.  If you're sure of the type, it should just be a regular cast.