Re: [PATCH v6] coresight: etm4x: avoid build failure with unrolled loops

On 10/07/2022 20:13, Arnd Bergmann wrote:

On Sat, Jul 9, 2022 at 1:15 AM Nick Desaulniers ndesaulniers@google.com wrote:

...

     ({                                                                      \
             u64 __val;                                                      \
                                                                             \

•           if (__builtin_constant_p((offset)))                             \
  

•           if (__is_constexpr((offset)))                                   \
                     __val = read_etm4x_sysreg_const_offset((offset));       \
             else                                                            \
                     __val = etm4x_sysreg_read((offset), true, (_64bit));    \
  
  

This is clearly better than the current version using __builtin_constant_p(), but I don't think it's safe in all cases, since there are expressions that are constant expressions to the compiler but are not valid input to the assembler.

I would prefer to see this fixed differently, but doing this one first is also fine with me:

Acked-by: Arnd Bergmann arnd@arndb.de

     Arnd

Thanks, I have queued this.

Suzuki