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From: "jamborm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/108226] __restrict on inlined function parameters does not
 function as expected
Date: Fri, 17 Feb 2023 13:57:27 +0000
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X-Bugzilla-Component: ipa
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108226

--- Comment #2 from Martin Jambor <jamborm at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
>=20
> so somehow the restrict qualification pessimizes IPA-CP?!  Martin?
>=20

Well, funny thing.  Without restrict, IPA-CP sees (from release_ssa dump):

void Func3 (char * p1, int * p2)
{
  <bb 2> [local count: 1073741824]:
  *p1_3(D) =3D 123;
  *p2_2(D) =3D 1;
  Func1 (p1_3(D), p2_2(D));
  return;
}

But with restrict in Func2 parameters, Func3 becomes:

void Func3 (char * p1, int * p2)
{
  <bb 2> [local count: 1073741824]:
  *p2_2(D) =3D 1;
  *p1_4(D) =3D 123;
  Func1 (p1_4(D), p2_2(D));
  return;
}

And the different ordering of the two stores is the problem, even when
p1 is not a char pointer, because we dont't trust the types of the
actual/formal parameters for TBAA (we would need to know in what types
they are read in Func1).=