[PATCH] Protection against stack-based memory corruption errors using SafeStack

[Volodymyr Kuznetsov]

Yes, running SafeStack with opt would certainly simplify debugging.
However, we want to apply the SafeStack transformation as the very last
step before code generation, to make sure that it operate on the final
stack layout. Doing so earlier might prevent some other optimizations from
succeeding (as it e.g., complicates the alias analysis, breaks mem2reg
pass, etc.) or might force the SafeStack pass move more objects to the
unsafe stack than necessary (e.g., if the operations on such objects that
the SafeStack considered potentially unsafe are actually later optimized
away). In principle, in some pathological cases, it might even break
correctness, e.g., if the SafeStack decides to keep some object on the
normal stack, but the subsequent optimization or instrumentation passes add
potentially unsafe operations on such objects.

http://reviews.llvm.org/D6094