[Bug tree-optimization/50346] Function call foils VRP/jump-threading of redundant predicate on struct member

[scovich at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50346

--- Comment #4 from Ryan Johnson <scovich at gmail dot com> 2011-10-12 12:40:25 UTC ---
(In reply to comment #3)
> Well, it's a tree optimization issue.  It's simple - the local aggregate f
> escapes the function via the member function call to baz:
> 
> <bb 5>:
>   foo::baz (&f);
> 
> and as our points-to analysis is not flow-sensitive for memory/calls this
> causes f to be clobbered by the call to bar

Is flow-sensitive analysis within single functions prohibitively expensive? All
the papers I can find talk about whole-program analysis, where it's very
expensive in both time and space; the best I could find (CGO'11 best paper)
gets it down to 20-30ms and 2-3MB per kLoC for up to ~300kLoC. 

>
> as neither the bodies of baz nor bar are visible there is nothing we can do

Would knowing the body of bar() help if the latter cannot be inlined?