From: Jason Merrill <jason@redhat.com>
Date: Mon, 5 Mar 2018 14:28:15 +0000 (-0500)
Subject: PR c++/84686 - missing volatile loads.
X-Git-Tag: releases/gcc-6.5.0~484
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=06381d0ac641d7644c90f75fddebc151acaed8c2;p=thirdparty%2Fgcc.git

PR c++/84686 - missing volatile loads.

	* cvt.c (convert_to_void): Call maybe_undo_parenthesized_ref.

From-SVN: r258246
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ab5a911f44ff..763a6947ec25 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/84686 - missing volatile loads.
+	* cvt.c (convert_to_void): Call maybe_undo_parenthesized_ref.
+
 2018-03-02  Jason Merrill  <jason@redhat.com>
 
 	PR c++/84489 - dependent default template argument
diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 0d1048cd7fe4..43fcff9854ea 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -932,6 +932,8 @@ convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain)
       || TREE_TYPE (expr) == error_mark_node)
     return error_mark_node;
 
+  expr = maybe_undo_parenthesized_ref (expr);
+
   if (implicit == ICV_CAST)
     mark_exp_read (expr);
   else
diff --git a/gcc/testsuite/g++.dg/tree-ssa/volatile2.C b/gcc/testsuite/g++.dg/tree-ssa/volatile2.C
new file mode 100644
index 000000000000..bec604424776
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/volatile2.C
@@ -0,0 +1,20 @@
+// PR c++/84686
+// { dg-additional-options -fdump-tree-gimple }
+// { dg-final { scan-tree-dump-times "= i" 10 "gimple" } }
+
+volatile int i;
+
+int main()
+{
+  i; //evaluated (a load is performed)
+  (i); //unevaluated => the load shall be performed
+
+  (void)i; //evaluated (a load is performed)
+  (void)(i); //unevaluated => the load shall be performed
+
+  (void)i; //evaluated (a load is performed)
+  (void)(i); //unevaluated => the load shall be performed
+
+  (i,i); // the two subexpression are evaluated
+  ((i),(i)); // no evaluation, => two loads shall happen
+}