[Bug tree-optimization/36010] New: Loop interchange not performed

[rguenth at gcc dot gnu dot org]

For the testcase

double a[16][64], y[64], x[16];
void foo(void)
{
  int i, j;
  for (j = 0; j < 64; ++j)
    for (i = 0; i < 16; ++i)
      y[j] = y[j] + a[i][j] * x[i];
}

with -O2 -fno-tree-pre -fno-tree-loop-im -ftree-loop-linear loop interchange
is performed but with PRE or lim moving the load (and the store) from/to
y[j] out of the innermost loop the interchange is no longer performed because

      before = gcc_loopnest_to_lambda_loopnest (loop_nest, &oldivs,
                                                &invariants, &lambda_obstack);

returns NULL.


-- 
           Summary: Loop interchange not performed
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36010