tree-optimization/109139 - fix .DEFERRED_INIT removal

The following make sure to strip MEMs when looking for unused
decls on the LHS of .DEFERRED_INIT.

	PR tree-optimization/109139
	* tree-ssa-live.cc (remove_unused_locals): Look at the
	base address for unused decls on the LHS of .DEFERRED_INIT.

	* gcc.dg/torture/pr109139.c: New testcase.

gcc/testsuite/gcc.dg/torture/pr109139.c

@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftrivial-auto-var-init=zero" } */
+
+const int COMPARE_CANDIDATE;
+char ipmi_ek_compare_link_record1_0, ipmi_ek_compare_link_record2_0;
+void ipmi_ek_compare_link()
+{
+  for (; ipmi_ek_compare_link_record1_0;)
+    for (; ipmi_ek_compare_link_record2_0;) {
+	int link[COMPARE_CANDIDATE];
+    }
+}

gcc/tree-ssa-live.cc

@@ -897,7 +897,8 @@ remove_unused_locals (void)
 	    else if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT))
 	      {
 		tree lhs = gimple_call_lhs (stmt);
-		if (DECL_P (lhs) && !is_used_p (lhs))
+		tree base = get_base_address (lhs);
+		if (DECL_P (base) && !is_used_p (base))
 		  {
 		    unlink_stmt_vdef (stmt);
 		    gsi_remove (&gsi, true);