[tree-ssa][PATCH]: Alias stats

[Daniel Berlin]

>
> But in terms of percentages, the queries vs resolved of each alias 
> info provider here are average for the bootstrap of gcc (IE pta 
> resolves about 80% of queries thrown at it, tbaa, about 50% thrown at 
> it).
>
> I'll be working the PTA results into other info soon (like using PTA 
> to determine if a variable accesses global memory, or is actually call 
> clobbered), which hopefully should increase our spec scores some.
>
>
I forgot to mention. PTA seems to do even better on C++ than it does C 
(which it does pretty well).

For example, on gerald's testcase, some of the numbers are like this:

Total alias queries:    64054
Total alias mayalias results:   368
Total alias noalias results:    63686
Total simple queries:   64054
Total simple resolved:  91
Total pointer TBAA queries:     2347
Total pointer TBAA resolved:    25
Total TBAA queries:     63938
Total TBAA resolved:    14855
Total PTA queries:      49083
Total PTA resolved:     48715


That's 99.2% of the PTA queries returning no alias, where TBAA only got 
23.2% of it's queries resolved to no alias.

Sometimes TBAA does better, but even then PTA still beats it percentage 
wise:

Total alias queries:    370012
Total alias mayalias results:   649
Total alias noalias results:    369363
Total simple queries:   370012
Total simple resolved:  193
Total pointer TBAA queries:     87699
Total pointer TBAA resolved:    27
Total TBAA queries:     369792
Total TBAA resolved:    289036
Total PTA queries:      80756
Total PTA resolved:     80107

(TBAA resolved 78%, PTA 99.2)
--Dan