ARM thumb2 does not propogate carry flag properly

[Alexey Starikovskiy]

information on carry flag is lost if gen_set_CF_bit31(t1) is called after logic operation.

[Peter Maydell (pmaydell)]

The existing code looks OK to me -- there's no need to call gen_set_CF_bit31() early because the inputs t0 and t1 to gen_thumb2_data_op() should always be distinct TCG values, and so gen_thumb2_data_op() will never trash t1. (There was a bug in this area involving ORN, but that was fixed in rev 29501f1, and I can see from your patch that you have that fix.)

Can you clarify which exact instruction, input data and output data case this patch is intended to fix, please?

[Alexey Starikovskiy (aystarik)]

MVNS with immediate fails in attached test program at 0x82c0 location. My patch fixes that.

[Peter Maydell (pmaydell)]

Current git master works for me on that test program without your patch:
cam-vm-266:maverick:qemu$ ./arm-linux-user/qemu-arm ~/Desktop/mvns_imm.exe
cam-vm-266:maverick:qemu$ echo $?
0

(I tested on qemu-0.14 just to confirm that I'm running the test program correctly, and that indeed fails as I would expect it to, exiting with status 255.)

Which qemu version have you been testing with?

[Alexey Starikovskiy (aystarik)]

0.15.0 fails for me.

On Mon, Oct 17, 2011 at 10:06 PM, Peter Maydell
<email address hidden> wrote:
> Current git master works for me on that test program without your patch:
> cam-vm-266:maverick:qemu$ ./arm-linux-user/qemu-arm ~/Desktop/mvns_imm.exe
> cam-vm-266:maverick:qemu$ echo $?
> 0
>
> (I tested on qemu-0.14 just to confirm that I'm running the test program
> correctly, and that indeed fails as I would expect it to, exiting with
> status 255.)
>
> Which qemu version have you been testing with?
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/874038
>
> Title:
>  ARM thumb2 does not propogate carry flag properly
>
> Status in QEMU:
>  New
>
> Bug description:
>  information on carry flag is lost if gen_set_CF_bit31(t1) is called
>  after logic operation.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/qemu/+bug/874038/+subscriptions
>

[Peter Maydell (pmaydell)]

> 0.15.0 fails for me.

Hmm. Works for me:

pm215@canth:/tmp$ wget http://wiki.qemu.org/download/qemu-0.15.0.tar.gz
[...]
pm215@canth:/tmp$ tar xzf qemu-0.15.0.tar.gz
pm215@canth:/tmp$ cd qemu-0.15.0/
pm215@canth:/tmp/qemu-0.15.0$ ./configure --target-list=arm-linux-user && make -j4
[...]
pm215@canth:/tmp/qemu-0.15.0$ ./arm-linux-user/qemu-arm ~/Desktop/mvns_imm.exe
pm215@canth:/tmp/qemu-0.15.0$ echo $?
0

[Alexey Starikovskiy (aystarik)]

Sorry for the noise, it appears I've checked on not clean 0.15.0