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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/94703] Small-sized  memcpy leading to unnecessary
 register spillage unless done through a dummy union
Date: Thu, 14 May 2020 09:49:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94703

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to ro@CeBiTec.Uni-Bielefeld.DE from comment #10)
> > --- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
> [...]
> > Hmm, OK looks like memcpy is not folded, likely because the source is
> > not known to be appropriately aligned.
> [...]
> > should fix this.  Can you verify and if so, commit?  Thx.
>=20
> Unfortunately, it doesn't.

OK, this only helps a bit later since CCP is required to propagate the
alignment, the following forwprop pass to elide the memcpy and then
finally the update-address-taken invocation in the _second_ CCP pass
after inlining will have

pr94703.c.093t.ccp2:No longer having address taken: r

I've long pondered to remove the memcpy folding restriction for strict-align
targets but never went through.

I'll update the testcase to require

/* { dg-require-effective-target non_strict_align } */=