[Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs -

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68050

            Bug ID: 68050
           Summary: SLP vectorization should negate constants to match up
                    + vs -
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
            Blocks: 53947
  Target Milestone: ---

double x[1024], y[1024], z[1024];
void foo (double w)
{
  int i;
  for (i = 0; i < 1023; i+=2)
    {
      z[i] = x[i] + 3.;
      z[i+1] = x[i+1] + -3.;
    }
}


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations