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From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/106187] armhf: Miscompilation at O2 level (O0 / O1 are
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Date: Mon, 25 Jul 2022 09:44:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106187

--- Comment #35 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
> There's no union involved here though but a memcpy used in BitCast.
Agreed, but by creating a shared stack slot, the compiler is effectively
creating a union of its own, and I think that needs to be accounted for.=20
update_alias_info_with_stack_vars handles the cases where we have pointers =
(at
the gimple level) into a shared stack slot, but doesn't (AFAICT) cater for =
RTL
lowering creating additional pointers (as it must since all objects on the
stack ultimately have to be addressed).

So if we create a shared stack slot for objects of different types, why do =
we
not also create an alias set for the combination of such types, much as we
would do for a union?=