This adjusts the loop interchange dependence checking to disallow
an outer loop dependence distance of zero.
2021-06-23 Richard Biener <rguenther@suse.de>
PR tree-optimization/101173
* gimple-loop-interchange.cc
(tree_loop_interchange::valid_data_dependences): Disallow outer
loop dependence distance of zero.
* gcc.dg/torture/pr101173.c: New testcase.
continue;
/* Be conservative, skip case if either direction at i_idx/o_idx
- levels is not '=' or '<'. */
- if (dist_vect[i_idx] < 0 || dist_vect[o_idx] < 0)
+ levels is not '=' (for the inner loop) or '<'. */
+ if (dist_vect[i_idx] < 0 || dist_vect[o_idx] <= 0)
return false;
}
}
--- /dev/null
+/* { dg-do run } */
+/* { dg-additional-options "-floop-interchange" } */
+
+int a[6][9];
+int main()
+{
+ a[1][3] = 8;
+ for (int b = 1; b <= 5; b++)
+ for (int d = 0; d <= 5; d++)
+#pragma GCC unroll 0
+ for (int c = 0; c <= 5; c++)
+ a[b][c] = a[b][c + 2] & 216;
+ for (int e = 0; e < 6; e++)
+ for (int f = 0; f < 9; f++)
+ if (a[e][f] != 0)
+ __builtin_abort ();
+ return 0;
+}