middle-end/101009 - fix distance vector recording

This fixes recording of distance vectors in case the DDR has just
constant equal indexes.  In that case we expect distance vectors
with zero distances to be recorded which is what was done when
any distance was computed for affine indexes.

2021-06-11  Richard Biener  <rguenther@suse.de>

	PR middle-end/101009
	* tree-data-ref.c (build_classic_dist_vector_1): Make sure
	to set *init_b to true when we encounter a constant equal
	index pair.
	(compute_affine_dependence): Also dump the actual DR_REF.

	* gcc.dg/torture/pr101009.c: New testcase.

(cherry picked from commit 336c41dbcb21740f8964021e157bc69ca547059b)

diff --git a/gcc/testsuite/gcc.dg/torture/pr101009.c b/gcc/testsuite/gcc.dg/torture/pr101009.c
new file mode 100644 (file)
index 0000000..2bbed1d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr101009.c
@@ -0,0 +1,17 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fno-tree-sra -fno-tree-pre -ftree-loop-distribution" } */
+
+struct a {
+  unsigned b;
+  unsigned c;
+} e, *f = &e;
+int d = 1;
+int main() {
+  for (; d; d--) {
+    struct a g[] = {{2, 1}, {2, 1}};
+    *f = g[1];
+  }
+  if (e.c != 1)
+    __builtin_abort ();
+  return 0;
+}

diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index e6dd5f15bedebf7d53954e8e8925a94b26102bea..d04e95f7c285bf3d80491bee37db4229f1a41c02 100644 (file)
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -5112,6 +5112,8 @@ build_classic_dist_vector_1 (struct data_dependence_relation *ddr,
          non_affine_dependence_relation (ddr);
          return false;
        }
+      else
+       *init_b = true;
     }
 
   return true;
@@ -5607,9 +5609,13 @@ compute_affine_dependence (struct data_dependence_relation *ddr,
   if (dump_file && (dump_flags & TDF_DETAILS))
     {
       fprintf (dump_file, "(compute_affine_dependence\n");
-      fprintf (dump_file, "  stmt_a: ");
+      fprintf (dump_file, "  ref_a: ");
+      print_generic_expr (dump_file, DR_REF (dra));
+      fprintf (dump_file, ", stmt_a: ");
       print_gimple_stmt (dump_file, DR_STMT (dra), 0, TDF_SLIM);
-      fprintf (dump_file, "  stmt_b: ");
+      fprintf (dump_file, "  ref_b: ");
+      print_generic_expr (dump_file, DR_REF (drb));
+      fprintf (dump_file, ", stmt_b: ");
       print_gimple_stmt (dump_file, DR_STMT (drb), 0, TDF_SLIM);
     }