tree-optimization/120817 - bogus DSE of .MASK_STORE

DSE used ao_ref_init_from_ptr_and_size for .MASK_STORE but
alias-analysis will use the specified size to disambiguate
against smaller objects.  For .MASK_STORE we instead have to
make the access size unspecified but we can still constrain
the access extent based on the maximum size possible.

	PR tree-optimization/120817
	* tree-ssa-dse.cc (initialize_ao_ref_for_dse): Use
	ao_ref_init_from_ptr_and_range with unknown size for
	.MASK_STORE and .MASK_LEN_STORE.

	* gcc.dg/vect/pr120817.c: New testcase.

2 files changed, 44 insertions, 4 deletions

diff --git a/gcc/testsuite/gcc.dg/vect/pr120817.c b/gcc/testsuite/gcc.dg/vect/pr120817.c
new file mode 100644
index 0000000..d8f55c9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr120817.c
@@ -0,0 +1,40 @@
+/* { dg-additional-options "-O1" } */
+/* { dg-additional-options "-mcpu=neoverse-n2" { target aarch64*-*-* } } */
+
+#include "tree-vect.h"
+
+typedef struct {
+    int _M_current;
+} __normal_iterator;
+
+typedef struct {
+    char _M_elems[5];
+} array_5;
+
+__normal_iterator __trans_tmp_1 = {-5};
+
+__attribute__((noipa))
+array_5 copySourceIntoTarget() {
+    array_5 target;
+    char* target_it = target._M_elems;
+
+    while (__trans_tmp_1._M_current != 0) {
+        *target_it = 1;
+        __trans_tmp_1._M_current++;
+        target_it++;
+    }
+
+    return target;
+}
+
+int main ()
+{
+  check_vect ();
+
+  array_5 res = copySourceIntoTarget();
+
+#pragma GCC novector
+  for (int i = 0; i < 5; i++)
+    if (res._M_elems[i] != 1)
+      __builtin_abort ();
+}
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 5ac4280..51a5723 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -181,10 +181,10 @@ initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write, bool may_def_ok = false)
 	       can provide a may-def variant.  */
 	    if (may_def_ok)
 	      {
-		ao_ref_init_from_ptr_and_size (
-		  write, gimple_call_arg (stmt, 0),
-		  TYPE_SIZE_UNIT (
-		    TREE_TYPE (gimple_call_arg (stmt, stored_value_index))));
+		ao_ref_init_from_ptr_and_range (
+		  write, gimple_call_arg (stmt, 0), true, 0, -1,
+		  tree_to_poly_int64 (TYPE_SIZE (
+		    TREE_TYPE (gimple_call_arg (stmt, stored_value_index)))));
 		return true;
 	      }
 	    break;