[PATCH] Debug info: Support fragmented variables.

[Adrian Prantl]

On Feb 26, 2014, at 3:06, Chandler Carruth <chandlerc at gmail.com> wrote:


Thanks for the review, Chandler! Your comments raise good points and I will address them in the next revision.

Regarding this one: 

> Comment at: lib/Transforms/Scalar/SROA.cpp:426-429
> @@ -419,1 +425,6 @@
> 
> +    // Make a best effort to find a dbg.declare intrinsic describing
> +    // the alloca by peeking at the next instruction.
> +    if (DbgDeclareInst *DDI=dyn_cast_or_null<DbgDeclareInst>(SI.getNextNode()))
> +      S.DbgDeclare = DDI;
> +
> ----------------
> This seems like a total hack.
> 
> It papers over the fact that this is not relevant for a particular store, but for the entire alloca.
> 
> Why can't we find this by locating the use of the alloca in the metadata and then the intrinsic using the metadata? I know it's a non-standard edge in the IR, but I was pretty sure it was still *an* edge in the IR somewhere that would let us find this?
> 


Eric or David,

_is_ there a canonical way to find a debug declare intrinsic for a specific alloca? I had this problem before, and the best I could come up with was to scan through every instruction and then check whether it is a debug intrinsic and describes that alloca, but IMO that’s too expensive, which is why I write code like the snippet above.

thanks,
Adrian