[LLVMdev] Request for comments: TBAA on call

[Chris Lattner]

On Oct 7, 2013, at 11:49 PM, Daniel Berlin <dberlin at dberlin.org> wrote:
> 
> Hence it’s more meaningful to reason about TBAA in terms of its semantics rather than hypothesizing about how and why someone would produce it.
> 
> That would be great, but it's not what the langref says, nor does it match up with the name of the thing you are creating, nor does it necessarily have optimal semantics, nor would it be great for future producers or the ability to do other analyses in those producers.

Hey Daniel,

Can you be more specific about your concerns here?  It's true that we describe the TBAA nodes in terms of expression C-like type constraints, but the intention of the design has always been for it to be more general.  

Specifically, partitioning the heap for use-cases like what Phil is doing with Javascript was factored into the original design.  We have even talked about adding type tags to represent C++ vtables (for example) since language loads and stores can't touch them (not even through char*).

The datastructures and algorithms we have are powerful enough to express these sorts of things, and so long as a frontend abided by the rules, there shouldn't be a problem.

-Chris 
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