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tree-optimization/101173 - fix interchange dependence checking 

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.
This commit is contained in:
Richard Biener 2021-06-23 09:59:28 +02:00
parent 3f1a08d9d7
commit 0ad9d88a3d
2 changed files with 20 additions and 2 deletions
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4
gcc/gimple-loop-interchange.cc
View File

@ -1043,8 +1043,8 @@ tree_loop_interchange::valid_data_dependences (unsigned i_idx, unsigned o_idx,
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;
}
}

18
gcc/testsuite/gcc.dg/torture/pr101173.c Normal file
View File

@ -0,0 +1,18 @@
/* { 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;
}