Backport fix for PR 65210 to gcc-5-branch

[Senthil Kumar Selvaraj <senthil_kumar.selvaraj@atmel.com>]

Hi,

  Is it ok to backport PR 65210 to gcc-5-branch? The patch is already in
  6.x and trunk.

Regards
Senthil

gcc/ChangeLog

2016-09-22  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	Backport from trunk r227496

	PR target/65210
	* config/avr/avr.c (avr_eval_addr_attrib): Look for io_low
	attribute as well.

gcc/testsuite/ChangeLog

2016-09-22  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	Backport from trunk r227496

	PR target/65210
	* gcc.target/avr/pr65210.c: New test.

Index: gcc/config/avr/avr.c
===================================================================
--- gcc/config/avr/avr.c	(revision 240340)
+++ gcc/config/avr/avr.c	(working copy)
@@ -9122,6 +9122,8 @@
       if (SYMBOL_REF_FLAGS (x) & SYMBOL_FLAG_IO)
 	{
 	  attr = lookup_attribute ("io", DECL_ATTRIBUTES (decl));
+	  if (!attr || !TREE_VALUE (attr))
+	    attr = lookup_attribute ("io_low", DECL_ATTRIBUTES (decl));
 	  gcc_assert (attr);
 	}
       if (!attr || !TREE_VALUE (attr))
       Index: gcc/testsuite/gcc.target/avr/pr65210.c
===================================================================
--- gcc/testsuite/gcc.target/avr/pr65210.c	(nonexistent)
+++ gcc/testsuite/gcc.target/avr/pr65210.c	(working copy)
@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+
+/* This testcase exposes PR65210. Usage of the io_low attribute
+   causes assertion failure because code only looks for the io
+   attribute if SYMBOL_FLAG_IO is set. */
+
+volatile char q __attribute__((io_low,address(0x81)));