[gcc r14-5554] Revert "tree-optimization/112281 - loop distribution and zero dependence distances"

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:1f28b2e4d8f8ea54848c332c707fa4ca5f028fa1

commit r14-5554-g1f28b2e4d8f8ea54848c332c707fa4ca5f028fa1
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Nov 17 14:47:07 2023 +0100

    Revert "tree-optimization/112281 - loop distribution and zero dependence distances"
    
    This reverts commit 5ea2965b499f9e491e45db19fedbccfccb75076a.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr112281.c | 19 -------------------
 gcc/tree-loop-distribution.cc           |  7 +++----
 2 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr112281.c b/gcc/testsuite/gcc.dg/torture/pr112281.c
deleted file mode 100644
index 3f0a61a9376..00000000000
--- a/gcc/testsuite/gcc.dg/torture/pr112281.c
+++ /dev/null
@@ -1,19 +0,0 @@
-/* { dg-do run } */
-/* { dg-additional-options "-ftree-loop-distribution" } */
-
-struct {
-  int : 8;
-  int a;
-} b, d[4] = {{0}, {0}, {0}, {5}};
-int c, e;
-int main()
-{
-  for (c = 2; c; c--)
-    for (e = 0; e < 2; e++) {
-      d[c] = b = d[c + 1];
-      d[c + 1].a = 0;
-    }
-  if (b.a != 0)
-    __builtin_abort();
-  return 0;
-}
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index 5ededd97c3d..ffca535064b 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -2163,10 +2163,9 @@ loop_distribution::pg_add_dependence_edges (struct graph *rdg, int dir,
 		 gcc.dg/tree-ssa/pr94969.c.  */
 	      if (DDR_NUM_DIST_VECTS (ddr) != 1)
 		this_dir = 2;
-	      /* If the dependence distance is zero in the innermost
-		 loop preserve stmt order.  */
-	      else if (DDR_DIST_VECT (ddr, 0)
-			 [DDR_LOOP_NEST (ddr).length () - 1] == 0)
+	      /* If the overlap is exact preserve stmt order.  */
+	      else if (lambda_vector_zerop (DDR_DIST_VECT (ddr, 0),
+					    DDR_NB_LOOPS (ddr)))
 		;
 	      /* Else as the distance vector is lexicographic positive swap
 		 the dependence direction.  */