[RS6000] Out-of-line register save functions can't be used from crtend.o

	PR target/45053
	* config/rs6000/t-crtstuff (CRTSTUFF_T_CFLAGS): Add -O2.

From-SVN: r246749

libgcc/ChangeLog

+2017-04-07  Alan Modra  <amodra@gmail.com>
+
+	PR target/45053
+	* config/rs6000/t-crtstuff (CRTSTUFF_T_CFLAGS): Add -O2.
+
 2017-04-03  Jonathan Wakely  <jwakely@redhat.com>
 
 	* config/c6x/pr-support.c (__gnu_unwind_execute): Fix typo in comment.

libgcc/config/rs6000/t-crtstuff

 # If .sdata is enabled __CTOR_{LIST,END}__ go into .sdata instead of
 # .ctors.
-CRTSTUFF_T_CFLAGS = -msdata=none
+# Do not build crtend.o with -Os as that can result in references to
+# out-of-line register save/restore functions, which may be unresolved
+# as crtend.o is linked after libgcc.a.  See PR45053.
+CRTSTUFF_T_CFLAGS = -msdata=none -O2