tree-optimization/101173 - fix interchange dependence checking

This adjusts the loop interchange dependence checking to properly
guard all dependence checks with DDR_REVERSED_P or its inverse.

2021-07-07  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/101173
	PR tree-optimization/101280
	* gimple-loop-interchange.cc
	(tree_loop_interchange::valid_data_dependences): Properly
	guard all dependence checks with DDR_REVERSED_P or its
	inverse.

	* gcc.dg/torture/pr101173.c: New testcase.

diff --git a/gcc/gimple-loop-interchange.cc b/gcc/gimple-loop-interchange.cc
index f45b9364644413d0502ca1313a2fbf7e230d28d6..7b799eca805ce331ef3514d8b6cea53c7a61b5a2 100644 (file)
--- a/gcc/gimple-loop-interchange.cc
+++ b/gcc/gimple-loop-interchange.cc
@@ -1044,7 +1044,10 @@ tree_loop_interchange::valid_data_dependences (unsigned i_idx, unsigned o_idx,
 
          /* 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)
+         if ((!DDR_REVERSED_P (ddr) && dist_vect[i_idx] < 0)
+             || (DDR_REVERSED_P (ddr) && dist_vect[i_idx] > 0)
+             || (!DDR_REVERSED_P (ddr) && dist_vect[o_idx] < 0)
+             || (DDR_REVERSED_P (ddr) && dist_vect[o_idx] > 0))
            return false;
        }
     }

diff --git a/gcc/testsuite/gcc.dg/torture/pr101173.c b/gcc/testsuite/gcc.dg/torture/pr101173.c
new file mode 100644 (file)
index 0000000..0c9090d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr101173.c
@@ -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;
+}

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loop-interchange-16.c b/gcc/testsuite/gcc.dg/tree-ssa/loop-interchange-16.c
new file mode 100644 (file)
index 0000000..781555e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/loop-interchange-16.c
@@ -0,0 +1,22 @@
+/* PR/101280 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-linterchange-details" } */
+
+void dummy (double *, double *);
+#define LEN_2D 32
+double aa[LEN_2D][LEN_2D], bb[LEN_2D][LEN_2D];
+double s231(int iterations)
+{
+//    loop interchange
+//    loop with data dependency
+    for (int nl = 0; nl < 100*(iterations/LEN_2D); nl++) {
+        for (int i = 0; i < LEN_2D; ++i) {
+            for (int j = 1; j < LEN_2D; j++) {
+                aa[j][i] = aa[j - 1][i] + bb[j][i];
+            }
+        }
+        dummy(aa[0],bb[0]);
+    }
+}
+
+/* { dg-final { scan-tree-dump "loops interchanged" "linterchange" } } */