Check STATIC_BMI2 instead of __BMI2__

[pps83]

ZSTD_ENABLE_ASM_X86_64_BMI2 already implies BMI2 by its name, and by the way it tests defines

[Cyan4973]

Looking at the definition of ZSTD_ENABLE_ASM_X86_64_BMI2,
it appears it does not imply the presence of __BMI2__.

The full test is :

#if !defined(ZSTD_DISABLE_ASM) &&                       \
    ZSTD_ASM_SUPPORTED &&                               \
    defined(__x86_64__) &&                              \
    (DYNAMIC_BMI2 || defined(__BMI2__))

So, ZSTD_ENABLE_ASM_X86_64_BMI2 can be defined to 1 if DYNAMIC_BMI2 is set to 1 too,
even if __BMI2__ is not defined.

It follows that ZSTD_ENABLE_ASM_X86_64_BMI2 && defined(__BMI2__) is not the same test as ZSTD_ENABLE_ASM_X86_64_BMI2 alone.
So the proposed change is not obvious to validate.

The context into which this macro test is invoked is also a bit complex, or at least it's not trivial to me.
I just note that, before this block, there are other blocks also triggered by similar though different macro tests,
such as #if DYNAMIC_BMI2, and # if ZSTD_ENABLE_ASM_X86_64_BMI2,
and they do something similar, such as setting loopFn function pointer.

I would look for @terrelln guidance on this code block,
and in absence of such guidance, I would rather lean towards cautiousness and not validate the suggested modification.

[pps83]

Yep, you are right, it's not exact.

Please, ignore this one for now. Imo it should be refactored with STATIC_BMI instead

[pps83]

Please, ignore this one for now. Imo it should be refactored with STATIC_BMI instead

should be ok now.

[pps83]

linux-kernel fails with this error:

../linux/lib/zstd/compress/../common/portability_macros.h:66:11: error: "STATIC_BMI2" is not defined, evaluates to 0 [-Werror=undef]
   66 |       && !STATIC_BMI2

however, there is no STATIC_BMI2 on portability_macros.h:66 line

[Cyan4973]

Try to rebase your PR on top of latest dev branch commit