AGHI instruction sets wrong condition code

[Thomas Huth]

 Hi Richard,

while looking at an issue that Michael reported in IRC today 
(https://bugs.debian.org/987110) I noticed that the AGHI instructions 
behaves differently in TCG compared to a KVM guest:

With the KVM guest:

(gdb) p/x $r14
$1 = 0x3ffffffaa48
(gdb) p/x $pswm
$2 = 0x705000180000000
(gdb) x/1i $pc
=> 0x3fff7f99d6e <dl_main+22>: aghi    %r14,-32
(gdb) stepi
0x000003fff7f99d72      1357    in rtld.c
(gdb) p/x $r14
$3 = 0x3ffffffaa28
(gdb) p/x $pswm
$4 = 0x705200180000000

With the TCG guest:

(gdb) p/x $r14
$1 = 0x3ffffffaa48
(gdb) p/x $pswm
$2 = 0x705000180000000
(gdb) x/1i $pc
=> 0x3fff7f99d6e <dl_main+22>: aghi    %r14,-32
(gdb) stepi
0x000003fff7f99d72      1357    in rtld.c
(gdb) p/x $r14
$3 = 0x3ffffffaa28
(gdb) p/x $pswm
$4 = 0x705000180000000

As you can see, the PSW mask is different after the AGHI instruction, real 
hardware sets CC to 2, while TCG keeps it a 0.

I stared at the translate.c and cc_helper.c code for a while, but I can't 
quite figure it out ... if you've got some spare minutes, could you maybe 
have a look at this, too?

 Thanks,
  Thomas


PS: I guess it's not the bug causing the issue reported by Michael, since 
there is no instruction looking at the CC right after that AGHI