+Tony
On 10/28/20 1:57 PM, Thomas Huth wrote:
> On 28/10/2020 05.18, Chen Qun wrote:
>> The current "#ifdef TARGET_X86_64" statement affects
>> the compiler's determination of fall through.
>>
>> When using -Wimplicit-fallthrough in our CFLAGS, the compiler showed warning:
>> target/i386/translate.c: In function ‘gen_shiftd_rm_T1’:
>> target/i386/translate.c:1773:12: warning: this statement may fall through
>> [-Wimplicit-fallthrough=]
>> if (is_right) {
>> ^
>> target/i386/translate.c:1782:5: note: here
>> case MO_32:
>> ^~~~
>>
>> Reported-by: Euler Robot <euler.ro...@huawei.com>
>> Signed-off-by: Chen Qun <kuhn.chen...@huawei.com>
>> ---
>> Cc: Paolo Bonzini <pbonz...@redhat.com>
>> Cc: Richard Henderson <richard.hender...@linaro.org>
>> Cc: Eduardo Habkost <ehabk...@redhat.com>
>> ---
>> target/i386/translate.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/i386/translate.c b/target/i386/translate.c
>> index caea6f5fb1..4c353427d7 100644
>> --- a/target/i386/translate.c
>> +++ b/target/i386/translate.c
>> @@ -1777,9 +1777,9 @@ static void gen_shiftd_rm_T1(DisasContext *s, MemOp
>> ot, int op1,
>> } else {
>> tcg_gen_deposit_tl(s->T1, s->T0, s->T1, 16, 16);
>> }
>> - /* FALLTHRU */
>> -#ifdef TARGET_X86_64
>> + /* fall through */
>> case MO_32:
>> +#ifdef TARGET_X86_64
>> /* Concatenate the two 32-bit values and use a 64-bit shift. */
>> tcg_gen_subi_tl(s->tmp0, count, 1);
>> if (is_right) {
>
> The whole code here looks a little bit fishy to me ... in case TARGET_X86_64
> is defined, the MO_16 code falls through to MO_32 ... but in case it is not
> defined, it falls through to the default case that comes after the #ifdef
> block? Is this really the right thing here? If so, I think there should be
> some additional comments explaining this behavior.
>
> Richard, maybe you could help to judge what is right here...?
I think the previous discussion is this thread:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg632245.html
