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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102571] FAIL:
 libgomp.c/../libgomp.c-c++-common/atomic-21.c execution test
Date: Wed, 06 Oct 2021 10:20:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102571

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Workaround committed, so for OpenMP it shouldn't trigger anymore.
But for
int
foo (char *p)
{
  long double l =3D 0.0;
  __builtin_clear_padding (&l);
  return __builtin_memcpy (&l, p, sizeof (l));
}
it still can, similarly for <atomic> APIs on long double, _Complex long dou=
ble
etc.
Related to PR93270 which was also about DSE, but the other order, something
clearing the memory and then writing a long double over it (which due to hw
leaves the padding bits unchanged) and DSE removing the clearing before it.
Here it is a long double store of initializer_zerop followed by clearing of=
 the
padding bits and removes the clearing of the padding bits.=