gcc : c++11 : full support : eta?

[Chris Lattner]

On Feb 8, 2013, at 8:24 AM, Jeff Law <law@redhat.com> wrote:
>> I'm not quite sure that this clean split is possible, even after making
>> amends for template instantiation.  It's great for syntax-driven tools,
>> but once you move beyond that, you tend to ignore stuff like destructors
>> (or the cleanup attribute), life-times of temporaries etc., things which
>> are just not visible in an AST.  You have to reimplement many program
>> analysis algorithms typically part of compiler optimizers, after
>> lowering the AST to a less elaborate intermediate representation (a step
>> which requires a fair amount of knowledge about the language in question).
> There's always going to be some things that are best done with the raw ASTs and others which are best done when we've got a lowered IL, CFG, SSA graph, etc.
> 
> The big question is how well can you go from the output of clang into a lower level IR where you can do in depth analysis and how much you allow optimizers to perturb the results of the analysis.  One could argue that clang -> gimple would be a useful translator to allow the nice things from the clang front-end, but also still allow the more in-depth analysis done by our tree-ssa code.

FWIW, the Clang static analyzer uses just such a representation: it is a CFG formed out of AST nodes.

-Chris