Re: [PATCH v2] target/i386: Remove compilation errors when -Werror=maybe-uninitialized

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 22/12/22 09:18, Paolo Bonzini wrote:
> On 12/21/22 17:36, Eric Auger wrote:
>> To avoid compilation errors when -Werror=maybe-uninitialized is used,
>> replace 'case 3' by 'default'.
>>
>> Otherwise we get:
>>
>> ../target/i386/ops_sse.h: In function ‘helper_vpermdq_ymm’:
>> ../target/i386/ops_sse.h:2495:13: error: ‘r3’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>     2495 |     d->Q(3) = r3;
>>          |     ~~~~~~~~^~~~
>> ../target/i386/ops_sse.h:2494:13: error: ‘r2’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>     2494 |     d->Q(2) = r2;
>>          |     ~~~~~~~~^~~~
>> ../target/i386/ops_sse.h:2493:13: error: ‘r1’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>     2493 |     d->Q(1) = r1;
>>          |     ~~~~~~~~^~~~
>> ../target/i386/ops_sse.h:2492:13: error: ‘r0’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>     2492 |     d->Q(0) = r0;
>>          |     ~~~~~~~~^~~~

With what compiler? Is that a supported one?

>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Suggested-by: Stefan Weil <sw@weilnetz.de>
>> Fixes: 790684776861 ("target/i386: reimplement 0x0f 0x3a, add AVX")
>> ---
>>   target/i386/ops_sse.h | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/i386/ops_sse.h b/target/i386/ops_sse.h
>> index 3cbc36a59d..c442c8c10c 100644
>> --- a/target/i386/ops_sse.h
>> +++ b/target/i386/ops_sse.h
>> @@ -2466,7 +2466,7 @@ void helper_vpermdq_ymm(Reg *d, Reg *v, Reg *s, 
>> uint32_t order)
>>           r0 = s->Q(0);
>>           r1 = s->Q(1);
>>           break;
>> -    case 3:
>> +    default:
>>           r0 = s->Q(2);
>>           r1 = s->Q(3);
>>           break;
>> @@ -2484,7 +2484,7 @@ void helper_vpermdq_ymm(Reg *d, Reg *v, Reg *s, 
>> uint32_t order)
>>           r2 = s->Q(0);
>>           r3 = s->Q(1);
>>           break;
>> -    case 3:
>> +    default:
>>           r2 = s->Q(2);
>>           r3 = s->Q(3);
>>           break;
> 
> Queued, but this compiler sucks. :)

Can't we simply add a dumb 'default' case? So when reviewing we don't
have to evaluate 'default' means 3 here.

-- >8 --
--- a/target/i386/ops_sse.h
+++ b/target/i386/ops_sse.h
@@ -2470,6 +2470,8 @@ void helper_vpermdq_ymm(Reg *d, Reg *v, Reg *s, 
uint32_t order)
          r0 = s->Q(2);
          r1 = s->Q(3);
          break;
+    default:
+        qemu_build_not_reached();
      }
      switch ((order >> 4) & 3) {
      case 0:
@@ -2488,6 +2490,8 @@ void helper_vpermdq_ymm(Reg *d, Reg *v, Reg *s, 
uint32_t order)
          r2 = s->Q(2);
          r3 = s->Q(3);
          break;
+    default:
+        qemu_build_not_reached();
      }
      d->Q(0) = r0;
      d->Q(1) = r1;
---