From FEDORA_PATCHES Mon Sep 17 00:00:00 2001

From: Jan Kratochvil <jan.kratochvil@redhat.com>

Date: Sun, 4 Feb 2018 21:42:18 +0100

Subject: gdb-ppc64-stwux-tautological-compare.patch

;; Fix ppc64 stwux encoding as found by gcc-8.0 -Werror=tautological-compare.

[patch] ppc64: Fix stwux encoding

https://sourceware.org/ml/gdb-patches/2018-02/msg00058.html

with gcc-8.0.1-0.9.fc28.x86_64 I get:

../../gdb/rs6000-tdep.c: In function 'CORE_ADDR skip_prologue(gdbarch*, CORE_ADDR, CORE_ADDR, rs6000_framedata*)':

../../gdb/rs6000-tdep.c:1911:34: error: bitwise comparison always evaluates to false [-Werror=tautological-compare]

       else if ((op & 0xfc1f016a) == 0x7c01016e)

                ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~

The code is there since:

	commit 98f08d3d9b69b344bb8b0cd2a4bda1cf4d966e20

	Author: Kevin Buettner <kevinb@redhat.com>

	Date:   Thu May 29 19:47:14 2003 +0000

		    From Jimi X <jimix@watson.ibm.com>:

		    * rs6000-tdep.c (skip_prologue): Improve support for 64-bit code.

So I do not think we can find the original author.

https://www.ibm.com/support/knowledgecenter/en/ssw_aix_72/com.ibm.aix.alangref/idalangref_stwux_stux_instrs.htm

says

	bit 21 - 30 = 183

	Those are bits 1..10 in normal bit order: 183<<1 = 0x16e

gdb/ChangeLog

2018-02-04  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* rs6000-tdep.c (skip_prologue): Fix stwux encoding.

diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c

--- a/gdb/rs6000-tdep.c

+++ b/gdb/rs6000-tdep.c

@@ -1908,7 +1908,7 @@ skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR lim_pc,

 	  offset = fdata->offset;

 	  continue;

 	}

-      else if ((op & 0xfc1f016a) == 0x7c01016e)

+      else if ((op & 0xfc1f016e) == 0x7c01016e)

 	{			/* stwux rX,r1,rY */

 	  /* No way to figure out what r1 is going to be.  */

 	  fdata->frameless = 0;