re PR c/89872 (GCC does not generate read access to volatile compound literal)

	PR c/89872
	* gimplify.c (gimplify_compound_literal_expr): Don't optimize a
	non-addressable complit into its initializer if it is volatile.

	* gcc.dg/tree-ssa/pr89872.c: New test.

From-SVN: r270023

gcc/ChangeLog

+2019-03-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/89872
+	* gimplify.c (gimplify_compound_literal_expr): Don't optimize a
+	non-addressable complit into its initializer if it is volatile.
+
 2019-03-29  Roman Zhuykov  <zhroma@ispras.ru>
 
 	* opts-common.c (integral_argument): Set errno properly in one case.

gcc/gimplify.c

@@ -4665,6 +4665,7 @@ gimplify_compound_literal_expr (tree *expr_p, gimple_seq *pre_p,
      otherwise we'd generate a new temporary, and we can as well just
      use the decl we already have.  */
   else if (!TREE_ADDRESSABLE (decl)
+	   && !TREE_THIS_VOLATILE (decl)
 	   && init
 	   && (fallback & fb_lvalue) == 0
 	   && gimple_test_f (init))

gcc/testsuite/ChangeLog

+2019-03-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/89872
+	* gcc.dg/tree-ssa/pr89872.c: New test.
+
 2019-03-29  Roman Zhuykov  <zhroma@ispras.ru>
 
 	* gcc.dg/diag-sanity.c: New test.

gcc/testsuite/gcc.dg/tree-ssa/pr89872.c

+/* PR c/89872 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times " ={v} 1;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " ={v} 2;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " ={v} 3;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " ={v} 4;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " ={v} 0;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " ={v} " 10 "optimized" } } */
+
+void
+foo (void)
+{
+  (volatile int){1} + (volatile int){2};
+}
+
+void
+bar (void)
+{
+  (volatile int){3};
+}
+
+void
+baz (void)
+{
+  (volatile int){4} / (volatile int){0};
+}