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tree-optimization/113431 - wrong dependence with invariant load

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The vectorizer dependence analysis is confused with invariant loads
when figuring whether the circumstances are so that we preserve
scalar stmt execution order.  The following rectifies this.

	PR tree-optimization/113431
	* tree-vect-data-refs.cc (vect_preserves_scalar_order_p):
	When there is an invariant load we might not preserve
	scalar order.

	* gcc.dg/vect/pr113431.c: New testcase.
This commit is contained in:
Richard Biener 2024-01-17 14:05:42 +01:00
parent 0f38666680
commit b981d5c60b
2 changed files with 24 additions and 0 deletions
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18
gcc/testsuite/gcc.dg/vect/pr113431.c Normal file
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@ -0,0 +1,18 @@
/* { dg-additional-options "-O3 -fdump-tree-slp1-details" } */
#include "tree-vect.h"
int a[2][9];
int b;
int main()
{
check_vect ();
for (b = 0; b < 2; b++)
for (long e = 8; e > 0; e--)
a[b][e] = a[0][1] == 0;
if (a[1][1] != 0)
__builtin_abort ();
return 0;
}
/* { dg-final { scan-tree-dump-times "optimized: basic block part vectorized" 2 "slp1" { target vect_int } } } */

6
gcc/tree-vect-data-refs.cc
View file

@ -282,6 +282,12 @@ vect_preserves_scalar_order_p (dr_vec_info *dr_info_a, dr_vec_info *dr_info_b)
&& !STMT_VINFO_GROUPED_ACCESS (stmtinfo_b))
return true;
/* If there is a loop invariant read involved we might vectorize it in
the prologue, breaking scalar oder with respect to the in-loop store. */
if ((DR_IS_READ (dr_info_a->dr) && integer_zerop (DR_STEP (dr_info_a->dr)))
|| (DR_IS_READ (dr_info_b->dr) && integer_zerop (DR_STEP (dr_info_b->dr))))
return false;
/* STMT_A and STMT_B belong to overlapping groups. All loads are
emitted at the position of the first scalar load.
Stores in a group are emitted at the position of the last scalar store.