re PR c++/84704 (internal compiler error: gimplification failed)

	PR c++/84704
	* tree.c (stabilize_reference_1): Return save_expr (e) for
	STATEMENT_LIST even if it doesn't have side-effects.

	* g++.dg/debug/pr84704.C: New test.

From-SVN: r258470

gcc/ChangeLog

+2018-03-13  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/84704
+	* tree.c (stabilize_reference_1): Return save_expr (e) for
+	STATEMENT_LIST even if it doesn't have side-effects.
+
 2018-03-12  Jonathan Wakely  <jwakely@redhat.com>
 
 	* doc/invoke.texi (-mclflushopt): Fix spelling of option.

gcc/testsuite/ChangeLog

+2018-03-13  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/84704
+	* g++.dg/debug/pr84704.C: New test.
+
 2018-03-12  Renlin Li  <renlin.li@arm.com>
 
 	* gcc.target/aarch64/movi_hf.c: New.

gcc/testsuite/g++.dg/debug/pr84704.C

+// PR c++/84704
+// { dg-do compile }
+// { dg-options "-g -fcompare-debug -O2" }
+
+int a[1] = { 0 };
+
+void
+foo ()
+{
+  a[({ 0; })] %= 5;
+}

gcc/tree.c

@@ -4352,6 +4352,11 @@ stabilize_reference_1 (tree e)
   switch (TREE_CODE_CLASS (code))
     {
     case tcc_exceptional:
+      /* Always wrap STATEMENT_LIST into SAVE_EXPR, even if it doesn't
+	 have side-effects.  */
+      if (code == STATEMENT_LIST)
+	return save_expr (e);
+      /* FALLTHRU */
     case tcc_type:
     case tcc_declaration:
     case tcc_comparison: