Re: [PATCH] Fix aarch64 ftrace JIT condition testcase

Pierre Langlois
2016-04-13T10:00:25Z

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.

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?

Thanks again!
Pierre

>
> 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);
> }
>