Re: [Qemu-devel] [PATCH] util/cacheinfo: Fix warning generated by clang

[Richard Henderson]

On 06/30/2017 08:39 AM, Pranith Kumar wrote:
> Clang generates the following warning on aarch64 host:
>
>    CC      util/cacheinfo.o
> /home/pranith/qemu/util/cacheinfo.c:121:48: warning: value size does not match 
> register size specified by the constraint and modifier [-Wasm-operand-widths]
>          asm volatile("mrs\t%0, ctr_el0" : "=r"(ctr));
>                                                 ^
> /home/pranith/qemu/util/cacheinfo.c:121:28: note: use constraint modifier "w"
>          asm volatile("mrs\t%0, ctr_el0" : "=r"(ctr));
>                             ^~
>                             %w0

That is an absolutely stupid warning.  There's long precedent for the compiler 
choosing the prefix for you based on the type of the argument.

> Constraint modifier 'w' is not (yet?) accepted by gcc. Fix this by increasing 
> the ctr size.

Certainly it is -- since the beginning of time.


r~