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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109088] GCC does not always vectorize
 conditional reduction
Date: Wed, 15 Nov 2023 14:09:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109088

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, so this is for

int foo (int *a, int x)
{
  int sum =3D 0;
  for (int i =3D 0; i < 1024; ++i)
    if (a[i] < 10)
      sum =3D sum + a[i] + x;
  return sum;
}

transforming it to

int foo (int *a, int x)
{
  int sum =3D 0;
  for (int i =3D 0; i < 1024; ++i)
    {
      tem =3D a[i] + x;
      if (a[i] < 10)
        sum =3D sum + tem;
    }
  return sum;
}

note this is re-associating and thus not always valid.  It also executes
stmts unconditionally (also not always valid, for FP spurious exceptions
might be raised).=