Re: Compile problems w/gcc 9.4.0 in linux-next

[Ingo Molnar <mingo@kernel.org>]

* Ard Biesheuvel <ardb@kernel.org> wrote:

> > Interestingly, if DYNAMIC_BMI2 in 
> > lib/zstd/common/portability_macros.h is changed on line 61 to 
> > always be defined as 0, the compile problem in huf_compress.c goes 
> > away.
> 
> Without having looked at the crashing code, I suspect that the only 
> meaningful course of action here is to tweak the conditional logic 
> that defines DYNAMIC_BMI2 to only enable it for GCC >= 10.1 (assuming 
> those are unaffected) In any case, GCC 9.4 is not going to get fixed 
> in the field, so even if this gets fixed on the GCC side, we will 
> have to deal with it here.

Apparently all GCC < 11.0 versions are crashing.

Would something like the fix below work?

Thanks,

	Ingo

===============>

 lib/zstd/common/portability_macros.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/zstd/common/portability_macros.h b/lib/zstd/common/portability_macros.h
index 0e3b2c0a527d..0dde8bf56595 100644
--- a/lib/zstd/common/portability_macros.h
+++ b/lib/zstd/common/portability_macros.h
@@ -55,7 +55,7 @@
 #ifndef DYNAMIC_BMI2
   #if ((defined(__clang__) && __has_attribute(__target__)) \
       || (defined(__GNUC__) \
-          && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))) \
+          && (__GNUC__ >= 11))) \
       && (defined(__x86_64__) || defined(_M_X64)) \
       && !defined(__BMI2__)
   #  define DYNAMIC_BMI2 1