[PATCH] Fix infinite recursion bug in SROA

[Duncan P. N. Exon Smith]

On Jan 21, 2014, at 10:20 AM, James Molloy <James.Molloy at arm.com> wrote:

> Hi Chandler,
>  
> OK – sure. Attached is a patch that removes the early exits. Is it OK?
>  
> Cheers,
>  
> James
> 
> <sroa-findcommontype.diff>_______________________________________________
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Hi James,

Just a nitpick here.

> Index: lib/Transforms/Scalar/SROA.cpp
> ===================================================================
> --- lib/Transforms/Scalar/SROA.cpp	(revision 199673)
> +++ lib/Transforms/Scalar/SROA.cpp	(working copy)
> @@ -956,8 +956,10 @@
>  static Type *findCommonType(AllocaSlices::const_iterator B,
>                              AllocaSlices::const_iterator E,
>                              uint64_t EndOffset) {
> -  Type *Ty = 0;
> -  bool IgnoreNonIntegralTypes = false;
> +  Type *Ty = NULL;
> +  bool TyIsNotCommon = false;

I think TyIsCommon (= true) is a better name.  The double-negative at the end of
the function (i.e., !TyIsNotCommon) is hard to read.

> +    if (!UserTy || (Ty && UserTy != Ty))
> +      TyIsNotCommon = true;

Obviously, this changes to:
    
    if (!UserTy || (Ty && UserTy != Ty))
      TyIsCommon = false;

> +  // If there is a common type, return that. Else return the integral type,
> +  // if there was one.
> +  if (Ty && !TyIsNotCommon)
> +    return Ty;

Now you can say:

    if (Ty && TyIsCommon)
      return Ty;