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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108498] [11/12/13 Regression] ppc64 big
 endian generates uninitialized reads with -fstore-merging
Date: Tue, 24 Jan 2023 12:55:39 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108498

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly adjusted testcase for -O2 which actually aborts at runtime quite
reliably:

struct A
{
  signed char a1;
  int a2;
};

struct B
{
  struct A b1;
  unsigned char b2:1, b3:1, b4:2, b5:1, b6:1, b7[4];
};

struct C
{
  unsigned char c1;
  char c2;
  signed char c3;
  unsigned char c4, c5[4], c6:1, c7:1, c8:1, c9:3, c10:1;
  struct A c11;
  struct B c12[3];
};

static inline struct C
foo (unsigned char a, unsigned b, int c, struct A d,
     unsigned e, struct B f, struct B g, struct B h)
{
  struct C x
    =3D { .c1 =3D b, .c2 =3D 0, .c3 =3D c, .c6 =3D a, .c4 =3D e, .c7 =3D 0,
        .c8 =3D 0, .c9 =3D 7, .c10 =3D 0, .c5 =3D {0, 1, 2, 3}, .c11 =3D d,
        .c12 =3D {f, g, h} };
  return x;
}

static inline struct A
bar (int a, int b)
{
  struct A x =3D { .a1 =3D a, .a2 =3D b };
  return x;
}

static inline struct B
baz (struct A b1)
{
  struct B x =3D { .b1 =3D b1, .b6 =3D 0, .b5 =3D 0, .b7 =3D {0, 1, 2, 3}, =
.b2 =3D 0 };
  return x;
}

struct C
qux (void)
{
  const struct B a =3D baz (bar (0, 0));
  struct C b;
  struct B c[2];
  struct A d =3D { 0, 1 };
  c[0].b1.a1 =3D 0;
  c[0].b1.a2 =3D 2;
  c[1].b1.a1 =3D 4;
  c[1].b1.a2 =3D 8;
  return foo (0, 2, -1, d, 3, c[0], c[1], a);
}

__attribute__((noipa)) void
corge (struct C *x)
{
  char buf[1024];
  __builtin_memset (buf, 0xaa, sizeof (buf));
  asm volatile ("" : : "r" (buf));
  __builtin_memset (x, 0x55, sizeof (struct C));
  asm volatile ("" : : "r" (x));
}

int
main ()
{
  struct C x;
  corge (&x);
  x =3D qux ();
  if (x.c6 || x.c9 !=3D 7)
    __builtin_abort ();
}=