g++ and aliasing bools

[Mark Mitchell]

> What do you consider "proof"?

The sort of thing that appears in a computer science textbook when
proving that an algorithm is sound.  Or at least what is often called
a "sketch of a proof".

> What more than not causing any regressions are you looking for?

A proof that this is not an algorithmic mistake.  This
is an aspect of GCC that we can reason about formally; the semantics
of alias sets are reasonably well defined, and the semantics of the
C++ abstract machine are reasonably well defined in this regard, so
it should be reasonably possible to convince ourselves that this
change is safe in the abstract if it is.

--
Mark Mitchell                   mark@codesourcery.com
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