[analyzer] Fix performance of getTaintedSymbolsImpl() (#89606)

Previously the function
```
std::vector<SymbolRef> taint::getTaintedSymbolsImpl(ProgramStateRef State,
                                                    const MemRegion *Reg,
                                                    TaintTagType K,
                                                    bool returnFirstOnly)
```
(one of the 4 overloaded variants under this name) was handling element
regions in a highly inefficient manner: it performed the "also examine
the super-region" step twice. (Once in the branch for element regions,
and once in the more general branch for all `SubRegion`s -- note that
`ElementRegion` is a subclass of `SubRegion`.)

As pointer arithmetic produces `ElementRegion`s, it's not too difficult
to get a chain of N nested element regions where this inefficient
recursion would produce 2^N calls.

This commit is essentially NFC, apart from the performance improvements
and the removal of (probably irrelevant) duplicate entries from the
return value of `getTaintedSymbols()` calls.

Fixes #89045

0 files changed, 0 insertions, 0 deletions