On Mon, Apr 16, 2018 at 1:11 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> On Mon, Apr 16, 2018 at 12:50:29PM +0200, Thomas Schwinge wrote:
>> > +#define set_feature(f) \
>> > + if (f < 32) features |= (1U << f); else features2 |= (1U << (f - 32))
>> > if (edx & bit_CMOV)
>> > - features |= (1 << FEATURE_CMOV);
>> > + set_feature (FEATURE_CMOV);
>>
>> [...]/libgcc/config/i386/cpuinfo.c: In function 'get_available_features':
>> [...]/libgcc/config/i386/cpuinfo.c:278:60: warning: left shift count is
>> negative [-Wshift-count-negative]
>> if (f < 32) features |= (1U << f); else features2 |= (1U << (f - 32))
>> ^~
>> [...]/libgcc/config/i386/cpuinfo.c:281:5: note: in expansion of macro
>> 'set_feature'
>> set_feature (FEATURE_CMOV);
>> ^~~~~~~~~~~
>> [...]/libgcc/config/i386/cpuinfo.c:280:6: warning: suggest explicit
>> braces to avoid ambiguous 'else' [-Wdangling-else]
>> if (edx & bit_CMOV)
>> ^
>> [Many more.]
>
> Oops, missed these. All of the warnings are false positives (warn on dead
> code) or style warning (-Wdangling-else), not actual code bugs.
>
> The following patch fixes all the warnings without changing code generation,
> we are using set_feature with constant arguments only, so everything is
> folded properly anyway.
>
> Ok for trunk?
>
> 2018-04-16 Jakub Jelinek <ja...@redhat.com>
>
> PR target/84945
> * config/i386/cpuinfo.c (set_feature): Wrap into do while (0) to avoid
> -Wdangling-else warnings. Mask shift counts to avoid
> -Wshift-count-negative and -Wshift-count-overflow false positives.
OK.
Thanks,
Uros.
> --- libgcc/config/i386/cpuinfo.c.jj 2018-03-30 20:37:37.683185248 +0200
> +++ libgcc/config/i386/cpuinfo.c 2018-04-16 13:04:45.239490344 +0200
> @@ -275,7 +275,14 @@ get_available_features (unsigned int ecx
> }
>
> #define set_feature(f) \
> - if (f < 32) features |= (1U << f); else features2 |= (1U << (f - 32))
> + do \
> + { \
> + if (f < 32) \
> + features |= (1U << (f & 31)); \
> + else \
> + features2 |= (1U << ((f - 32) & 31)); \
> + } \
> + while (0)
>
> if (edx & bit_CMOV)
> set_feature (FEATURE_CMOV);
>
>
> Jakub
