Re: [PATCH] Fix aarch64 ftrace JIT condition testcase

[Antoine Tremblay <antoine dot tremblay at ericsson dot com>]

Pierre Langlois writes:

> Hi Antoine,
>
> On 12/04/16 16:13, Antoine Tremblay wrote:
>> This patch fixes the following failure:
>> FAIL: gdb.trace/trace-condition.exp: ftrace: -(21 << 1) == -42: check 10
>> frames were collected.
>> 
>> This was due to aarch64_emit_sub using the wrong order in its operands, so the
>> operation would end up being 42 - 0 rather than 0 - 42.
>
> Ooops, thanks for the fix!  I was a little confused how I could have
> missed this, it turns out I had forgotten to had parentheses in
> `-(21 << 1) == -42' at the time, so `emit_sub' was not tested here.

hehe.

>
> I aimed at testing `emit_sub' with the following test case which is
> clearly not good enough:
>
>   gdb.trace/trace-condition.exp: ftrace: 21 - 21 == 0
>
> Would you be OK with changing it to "42 - 21 == 21" or something?
>

Right indeed good idea, I'm sending a v2 with this.

> Thanks again!

np.

Antoine

>> This patch also fixes the order of aarch64_emit_add for clarity.
>> 
>> Tested on aarch64-native-extended-gdbserver.
>> 
>> Note: trace-condition.exp was broken a bit so I had to modify it to run
>> the test. A fix is coming for that in another patch.
>> 
>> gdb/gdbserver/ChangeLog:
>> 
>> 	* linux-aarch64-low.c (aarch64_emit_add): Switch x1 and x0.
>> 	(aarch64_emit_sub): Likewise.
>> ---
>>  gdb/gdbserver/linux-aarch64-low.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/gdb/gdbserver/linux-aarch64-low.c b/gdb/gdbserver/linux-aarch64-low.c
>> index 12fe2e6..d237bde 100644
>> --- a/gdb/gdbserver/linux-aarch64-low.c
>> +++ b/gdb/gdbserver/linux-aarch64-low.c
>> @@ -2258,7 +2258,7 @@ aarch64_emit_add (void)
>>    uint32_t *p = buf;
>>  
>>    p += emit_pop (p, x1);
>> -  p += emit_add (p, x0, x0, register_operand (x1));
>> +  p += emit_add (p, x0, x1, register_operand (x0));
>>  
>>    emit_ops_insns (buf, p - buf);
>>  }
>> @@ -2272,7 +2272,7 @@ aarch64_emit_sub (void)
>>    uint32_t *p = buf;
>>  
>>    p += emit_pop (p, x1);
>> -  p += emit_sub (p, x0, x0, register_operand (x1));
>> +  p += emit_sub (p, x0, x1, register_operand (x0));
>>  
>>    emit_ops_insns (buf, p - buf);
>>  }
>>