Fix for prologue processing on PowerPC

One of conditions in skip_prologue() was never visited if there was mflr
instruction that moves the link register to a register different than r0.
This condition expects non shifted value of `lr_reg`. Previously offset
of link register was never saved for registers different than r0.

gdb/ChangeLog:

2018-01-31  Nikola Prica  <nikola.prica@rt-rk.com>

	* rs6000-tdep.c (skip_prologue): Remove shifting for lr_reg and
	assign shifted lr_reg to fdata->lr_register when lr_reg is set.

gdb/testsuite/ChangeLog:

2018-01-31  Nikola Prica  <nikola.prica@rt-rk.com>

	* gdb.arch/powerpc-prologue-frame.s: New file.
	* gdb.arch/powerpc-prologue-frame.c: Likewise.
	* gdb.arch/powerpc-prologue-frame.exp: Likewise.

1 files changed, 28 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.arch/powerpc-prologue-frame.c b/gdb/testsuite/gdb.arch/powerpc-prologue-frame.c
new file mode 100644
index 0000000..8cab6f2
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/powerpc-prologue-frame.c
@@ -0,0 +1,28 @@
+/* This test is part of GDB, the GNU debugger.
+
+   Copyright 2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int bar()
+{
+  return 0;
+}
+
+int foo();
+
+int main(void)
+{
+  return foo();
+}