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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/103905] [12 Regression] Miscompiled i386-expand.c with
 -march=bdver1 and -O3 since r12-1789-g836328b2c99f5b8d
Date: Tue, 04 Jan 2022 21:31:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103905

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
>>From what I can see, ifcvt dump is the same between r12-1788 and r12-1789, =
vect
has quite a few changes in that function, but the function is fairly simple=
 in
ifcvt, because almost nothing is inlined into it, so there is just the sing=
le
  for (i =3D 0; i < nelt; ++i)
    d.perm[i] =3D i * 2 + odd;
loop in that function.

I see similar changes on reduced:
struct S { unsigned char perm[64]; };

void bar (struct S *);

void
foo (unsigned int nelt, unsigned odd)
{
  struct S d;
  unsigned i;

  for (i =3D 0; i < nelt; ++i)
    d.perm[i] =3D i * 2 + odd;

  bar (&d);
}

Do you know what nelt and odd values are used during the misbehaving
*_vec_even_odd on your testcase?  If so, perhaps we could make bar noipa and
add perm verification in there, make foo also noipa and just call it from m=
ain
with those arguments...=