re PR tree-optimization/80334 (Segfault when taking address of copy of unaligned struct)

2017-04-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80334
	* tree-ssa-loop-ivopts.c (rewrite_use_address): Properly
	preserve alignment of accesses.

	* g++.dg/torture/pr80334.C: New testcase.

From-SVN: r246731

gcc/ChangeLog

 2017-04-06  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/80334
+	* tree-ssa-loop-ivopts.c (rewrite_use_address): Properly
+	preserve alignment of accesses.
+
+2017-04-06  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/80262
 	* tree-sra.c (build_ref_for_offset): Preserve address-space
 	information.

gcc/testsuite/ChangeLog

+2017-04-06  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/80334
+	* g++.dg/torture/pr80334.C: New testcase.
+
 2017-04-06  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/80166

gcc/testsuite/g++.dg/torture/pr80334.C

+// { dg-do run }
+
+struct A { alignas(16) char c; };
+struct B { A unpacked; char d; } __attribute__((packed));
+
+char x;
+
+int
+main()
+{
+  alignas(16) B b[3];
+  for (int i = 0; i < 3; i++) b[i].unpacked.c = 'a' + i;
+  for (int i = 0; i < 3; i++)
+    {
+      auto a = new A(b[i].unpacked);
+      x = a->c;
+    }
+}

gcc/tree-ssa-loop-ivopts.c

@@ -7396,7 +7396,11 @@ rewrite_use_address (struct ivopts_data *data,
     base_hint = var_at_stmt (data->current_loop, cand, use->stmt);
 
   iv = var_at_stmt (data->current_loop, cand, use->stmt);
-  ref = create_mem_ref (&bsi, TREE_TYPE (*use->op_p), &aff,
+  tree type = TREE_TYPE (*use->op_p);
+  unsigned int align = get_object_alignment (*use->op_p);
+  if (align != TYPE_ALIGN (type))
+    type = build_aligned_type (type, align);
+  ref = create_mem_ref (&bsi, type, &aff,
 			reference_alias_ptr_type (*use->op_p),
 			iv, base_hint, data->speed);
   copy_ref_info (ref, *use->op_p);