Re: [Qemu-devel] assertion in temp_save

[Max Filippov]

On Tue, Nov 20, 2012 at 9:47 PM, Aurelien Jarno <address@hidden> wrote:
> On Tue, Nov 20, 2012 at 05:09:57AM +0300, Max Filippov wrote:
>> On Sun, Nov 18, 2012 at 7:34 AM, Max Filippov <address@hidden> wrote:
>> > On Sun, Nov 18, 2012 at 7:19 AM, Max Filippov <address@hidden> wrote:
>> >> Hi Aurelien,
>> >>
>> >> starting with commit 2c0366f tcg: don't explicitly save globals and temps
>> >> I get the following abort on target-xtensa:
>> >>
>> >> qemu-system-xtensa: tcg/tcg.c:1665: temp_save: Assertion
>> >> `s->temps[temp].val_type == 2 || s->temps[temp].fixed_reg' failed.
>> >> Aborted
>> >>
>> >> I see that that commit only adds assertion and that bad thing happens
>> >> elsewhere. I've found that removal of tcg_gen_discard_i32 in the
>> >> gen_right_shift_sar makes it work again. The trace of the TB that fails
>> >> translation is below. If 'discard loc5' is removed it starts to work.
>> >>
>> >> Any idea of what might be wrong?
>> >
>> > In the debugger loc5 looks like this when abort happens:
>> >
>> > (gdb) p s->temps[105]
>> > $2 = {
>> >   base_type = TCG_TYPE_I32,
>> >   type = TCG_TYPE_I32,
>> >   val_type = 0,
>> >   reg = 11,
>> >   val = 32,
>> >   mem_reg = 4,
>> >   mem_offset = 128,
>> >   fixed_reg = 0,
>> >   mem_coherent = 0,
>> >   mem_allocated = 0,
>> >   temp_local = 1,
>> >   temp_allocated = 0,
>> >   next_free_temp = -1,
>> >   name = 0x0
>> > }
>>
>> Looks like the issue is local temp reaching the end of TB in a dead state.
>> Hence the question: is discard applicable to local temps?
>> Or maybe I should just make it global (two other tcg values used with discard
>> in other targets are also globals) and avoid temp_local_new/temp_free at
>> first place?
>>
>
> Indeed, it looks like that discard doesn't work correctly with a temp
> local with this new patch. I might have a fix, but I would like to do
> some more tests first. Would it be possible to provide a way to reproduce
> the issue?

Here's the test case (xtensa assembler):

.section .init
.global _start
_start:
    ssl     a2
    ssr     a2
    j       _start

Sources + compiled version is available at
http://jcmvbkbc.spb.ru/~dumb/ws/osll/qemu-xtensa/20121120/

-- 
Thanks.
-- Max