[Bug tdep/30021] [gdb/tdep, powerpc64le] previous frame inner to this frame (corrupt stack?)

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30021

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cel at us dot ibm.com,
                   |                            |kevinb at redhat dot com,
                   |                            |ulrich.weigand at de dot ibm.com

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
With gcc 4.8.5, I'm running into FAILs in gdb.base/unwind-on-each-insn.exp,
which I assume are a duplicate of this one, for the reason that the same insn
triggers the problem:
...
FAIL: gdb.base/unwind-on-each-insn.exp: instruction 5: $fba_value == $main_fba
FAIL: gdb.base/unwind-on-each-insn.exp: instruction 5: [string equal $fid
$main_fid]
...

Disassembly of foo:
...
00000000100006dc <foo>:
    100006dc:   f8 ff e1 fb     std     r31,-8(r1)
    100006e0:   d1 ff 21 f8     stdu    r1,-48(r1)
    100006e4:   78 0b 3f 7c     mr      r31,r1
    100006e8:   30 00 3f 38     addi    r1,r31,48
    100006ec:   f8 ff e1 eb     ld      r31,-8(r1)
    100006f0:   20 00 80 4e     blr
...

Minimal reproducer:
...
$ gdb -q -batch outputs/gdb.base/unwind-on-each-insn/unwind-on-each-insn \
  -ex "set trace-commands on" \
  -ex "b *foo + 12" \
  -ex "display /x \$r1" \
  -ex "display /x \$r31" \
  -ex run \
  -ex "info frame" \
  -ex "si" \
  -ex "info frame" \
  -ex si \
  -ex "info frame"
+b *foo + 12
Breakpoint 1 at 0x100006e8
+display /x $r1
+display /x $r31
+run

Breakpoint 1, 0x00000000100006e8 in foo ()
1: /x $r1 = 0x7fffffffec80
2: /x $r31 = 0x7fffffffec80
+info frame
Stack level 0, frame at 0x7fffffffecb0:
 pc = 0x100006e8 in foo; saved pc = 0x100006b0
 called by frame at 0x7fffffffed20
 Arglist at 0x7fffffffec80, args: 
 Locals at 0x7fffffffec80, Previous frame's sp is 0x7fffffffecb0
 Saved registers:
  r31 at 0x7fffffffeca8
+si
0x00000000100006ec in foo ()
1: /x $r1 = 0x7fffffffecb0
2: /x $r31 = 0x7fffffffec80
+info frame
Stack level 0, frame at 0x7fffffffecb0:
 pc = 0x100006ec in foo; saved pc = 0x100006b0
 called by frame at 0x7fffffffecf0
 Arglist at 0x7fffffffec80, args: 
 Locals at 0x7fffffffec80, Previous frame's sp in r1
+si
0x00000000100006f0 in foo ()
1: /x $r1 = 0x7fffffffecb0
2: /x $r31 = 0x7fffffffecb0
+info frame
Stack level 0, frame at 0x7fffffffecb0:
 pc = 0x100006f0 in foo; saved pc = 0x100006b0
 called by frame at 0x7fffffffed20
 Arglist at 0x7fffffffecb0, args: 
 Locals at 0x7fffffffecb0, Previous frame's sp in r1
...

Note this line:
...
 called by frame at 0x7fffffffed20
  ...
 called by frame at 0x7fffffffecf0
  ...
 called by frame at 0x7fffffffed20
...

It's correct for the insn first insn (at 100006e8), which is not unwound by the
epilogue unwinder.

It's also correct for the last insn (at 100006f0), which is unwound by the
epilogue unwinder.

It not correct for the middle insn (at 100006ec), which is also unwound by the
epilogue unwinder.

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