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Re: Incorrect bitfield aliasing with Tree SSA
> Again, the tree level relies on the documented (in the comments of
> alias.c) fact that given a structure, the fields contained in a
> structure will have alias sets that are strict subsets of the parent.
That is ONLY true for fields that don't have DECL_NONADDRESSABLE_P
and that's been the case foreever. The documentation might be confusing,
but the code has never been.
> The bug reports are about cases where we have a struct foo * (where
> struct foo contains int a:31), and foo pointer->a is claimed to not
> alias with foo.a.
How can you take a pointer to the bitfield?
> I would much rather maintain the strict subset invariant than the
> component_uses_parent_alias_set stuff, since this is the documented
> invariant, and makes sense.
But throws away the entire DECL_NONADDRESSABLE_P mechanism! Also, how
do we handle TYPE_NONALIASED_COMPONENT? It's exactly the same issue?