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From: "linkw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102897] [12 Regression] simplify_permutation
 ICEs on assert since r12-1103-g4a9f2306cb39a3cf
Date: Mon, 25 Oct 2021 09:03:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102897

--- Comment #3 from Kewen Lin <linkw at gcc dot gnu.org> ---
The culprit assertion is based on one assumption, for one given VEC_PERM_EX=
PR
expression, if the type of permutation control vector and the type of
permutation operand is the same, and it's foldable, then it's done previous=
ly.
But from this case, this is not true.

For example, for the case

int8x8_t fn1(int8x8_t val20, char tmp) {
  int8x8_t __a =3D (int8x8_t){tmp};
  return __builtin_shuffle(__a, val20, (int8x8_t){0, 1, 2, 3, 4, 5, 6, 7});
}

we can get

int8x8_t fn1 (int8x8_t val20, char tmp)
{
  int8x8_t __a;

  <bb 2> :
  __a_2 =3D {tmp_1(D)};
  return __a_2;

}

before forwprop, while for the case

int8x8_t fn1(int8x8_t val20, char tmp) {
  int8x8_t __a =3D (int8x8_t){tmp};
  return __builtin_shuffle(__a, val20, (int8x8_t){0, 1, 2, 3, 0, 1, 2, 3});
}

we only get the below before forwprop,

int8x8_t fn1 (int8x8_t val20, char tmp)
{
  int8x8_t __a;
  int8x8_t _3;

  <bb 2> :
  __a_2 =3D {tmp_1(D)};
  _3 =3D VEC_PERM_EXPR <__a_2, __a_2, { 0, 1, 2, 3, 0, 1, 2, 3 }>;
  return _3;

}

After remove the assertion there, we can get below immediately at forwprop.

int8x8_t fn1 (int8x8_t val20, char tmp)
{
  int8x8_t __a;
  int8x8_t _3;

  <bb 2> :
  __a_2 =3D {tmp_1(D)};
  _3 =3D {tmp_1(D), 0, 0, 0, tmp_1(D), 0, 0, 0};
  return _3;

}

I think we should remove this assertion.=