[PATCH] gdb.trace: Fix string collection for 64-bit platforms.

["Marcin Kościelnicki" <koriakin@0x04.net>]

String collection always used ref32 to fetch the string pointer.  Make it
use ref64 when pointeer size is 64-bit.

This appeared to work on x86_64 since it's a little-endian platform, and
malloc (used in gdb.trace/collection.exp) returns addresses in low 4GB.
Noticed and tested on s390x-ibm-linux-gnu, also tested on
i686-unknown-linux-gnu and x86_64-unknown-linux-gnu.

gdb/ChangeLog:

	* ax-gdb.c (gen_traced_pop): Use aop_ref64 when appropriate for
	string collection.
---
OK to push?

 gdb/ChangeLog | 5 +++++
 gdb/ax-gdb.c  | 5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 45d8ef9..3f4d152 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2016-01-21  Marcin Kościelnicki  <koriakin@0x04.net>
+
+	* ax-gdb.c (gen_traced_pop): Use aop_ref64 when appropriate for
+	string collection.
+
 2016-01-21  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* disasm.c (maybe_add_dis_line_entry): Rename to...
diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index dd6eee6..d17cb04 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -410,7 +410,10 @@ gen_traced_pop (struct gdbarch *gdbarch,
 
 	  if (string_trace)
 	    {
-	      ax_simple (ax, aop_ref32);
+	      if (TYPE_LENGTH(value->type) == 4)
+	        ax_simple (ax, aop_ref32);
+	      else
+	        ax_simple (ax, aop_ref64);
 	      ax_const_l (ax, ax->trace_string);
 	      ax_simple (ax, aop_tracenz);
 	    }
-- 
2.7.0