[PATCH] tree-optimization/93586 - bogus path-based disambiguation

[Richard Biener]

This fixes bogus path-based disambiguation of mismatched array shape
accesses.

Bootstrap & regtest running on x86_64-unknown-linux-gnu.

Honza, is this the correct place to detect this or were we not
supposed to arrive there?

Thanks,
Richard.

2020-02-17  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/93586
        * tree-ssa-alias.c (nonoverlapping_array_refs_p): Fail when
        we're obviously not looking at same-shaped array accesses.

        * gcc.dg/torture/pr93586.c: New testcase.
---
 gcc/testsuite/gcc.dg/torture/pr93586.c | 21 +++++++++++++++++++++
 gcc/tree-ssa-alias.c                   |  5 +++++
 2 files changed, 26 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr93586.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr93586.c 
b/gcc/testsuite/gcc.dg/torture/pr93586.c
new file mode 100644
index 00000000000..e861bdcd78e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr93586.c
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fgimple" } */
+
+int __GIMPLE(ssa) foo(int j)
+{
+  int c[1][10][1];
+  int _1;
+
+__BB(2):
+  c[0][1][0] = 1;
+  c[0][1] = _Literal (int[1]) {};
+  _1 = c[0][j_2(D)][0];
+  return _1;
+}
+
+int main()
+{
+  if (foo (1) != 0)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index b8df66ac1f2..e7caf9bee77 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -1291,6 +1291,11 @@ nonoverlapping_array_refs_p (tree ref1, tree ref2)
 
   tree elmt_type1 = TREE_TYPE (TREE_TYPE (TREE_OPERAND (ref1, 0)));
   tree elmt_type2 = TREE_TYPE (TREE_TYPE (TREE_OPERAND (ref2, 0)));
+  /* If one element is an array but not the other there's an obvious
+     mismatch in dimensionality.  */
+  if ((TREE_CODE (elmt_type1) == ARRAY_TYPE)
+      != (TREE_CODE (elmt_type2) == ARRAY_TYPE))
+    return -1;
 
   if (TREE_OPERAND (ref1, 3))
     {
-- 
2.16.4