Re: [PATCH] Fix aarch64 ftrace JIT condition testcase

Antoine Tremblay
2016-04-13T12:26:39Z

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);
>> }
>>