ppc64: Fix stwux encoding
Commit Message
Hi,
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
OK for check-in?
Jan
gdb/ChangeLog
2018-02-04 Jan Kratochvil <jan.kratochvil@redhat.com>
* rs6000-tdep.c (skip_prologue): Fix stwux encoding.
Comments
On Sun, 4 Feb 2018 21:39:23 +0100
Jan Kratochvil <jan.kratochvil@redhat.com> wrote:
> 2018-02-04 Jan Kratochvil <jan.kratochvil@redhat.com>
>
> * rs6000-tdep.c (skip_prologue): Fix stwux encoding.
>
Okay.
On Mon, 05 Feb 2018 19:46:21 +0100, Kevin Buettner wrote:
> On Sun, 4 Feb 2018 21:39:23 +0100 Jan Kratochvil <jan.kratochvil@redhat.com> wrote:
> > 2018-02-04 Jan Kratochvil <jan.kratochvil@redhat.com>
> >
> > * rs6000-tdep.c (skip_prologue): Fix stwux encoding.
> >
>
> Okay.
Checked in:
72dd27306224497c8ba97f391d30b774d4d973fb
Jan
Thank you for this patch!
The mask was still too permissive (see PR gdb/18295), so I submitted
another patch fixing that. Sorry I didn't see this before!
Previously the stdux mask also allowed stwux (and more), and the if body
was the same, so it was accidentally working for stwux, despite the
tautological compare.
@@ -1857,7 +1857,7 @@ 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;