[PATCH] D51976: [DebugInfo][Dexter] Speculated BB presents illegal variable value to debugger

[Paul Robinson via Phabricator via llvm-commits]

probinson added a comment.

In https://reviews.llvm.org/D51976#1236852, @CarlosAlbertoEnciso wrote:

> In https://reviews.llvm.org/D51976#1235508, @aprantl wrote:
>
> > Having read the real testcase now, I understand why you are dropping the debug info now. I would like to point out that we could do better. If we extended llvm.dbg.value to take more than one LLVM SSA Value, then we could produce a DIExpression that selects either %add or %sub depending on the value of %cmp. Let me know if you are interested in implementing this, it should be relatively straight forward to do and would come in useful in all sorts of other situations, too.
>
>
> That is a very good idea and I am interested in implementing it. A good opportunity to improve my knowledge in that area. I can see the associated benefits.


Hi Carlos, I had this exact conversation with Tom Weaver last week.  Extending llvm.dbg.value to handle more complex expressions will allow huge steps forward in making variable values visible (if not always modifiable).  He was thinking more in terms of loop induction variables however.  Maybe you two can collaborate on the IR part of this.


https://reviews.llvm.org/D51976