[Bug target/96854] [10 Regression] avx vectorizer breaks complex arithmetic

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96854

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |needs-bisection
      Known to fail|                            |10.1.0, 10.2.0
      Known to work|                            |11.0, 9.3.0
     Ever confirmed|0                           |1
   Target Milestone|---                         |10.3
   Last reconfirmed|                            |2020-08-31
             Target|                            |x86_64-*-* i?86-*-*
            Summary|avx vectorizer breaks       |[10 Regression] avx
                   |complex arithmetic          |vectorizer breaks complex
                   |                            |arithmetic
                 CC|                            |rguenth at gcc dot gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
#include <complex.h>

double complex __attribute__((noipa))
foo(double complex acc, const double complex *x, const double complex* y, int
N)
{
  for (int c = 0; c < N; ++c)
    acc -= x[c] * y[c];
  return acc;
}

int main(void)
{
  static const double complex y[] = { 1, 2, };
  static const double complex x[] = { 1, 3, };

  double complex ref = foo(0, x, y, 2); // reference

  if (creal(ref) != -7.)
    __builtin_abort ();
  return 0;
}


Confirmed with GCC 10.2, it works on trunk and with GCC 9.3.0.

It doesn't need any -march for me, just -Ofast -mavx is enough.