gmp-6.1.0 on Cygwin

[ASSI]

[I'm the current Cygwin gmp maintainer.]

I've recently updated to gmp-6.1.0 on Cygwin and a few users have reported 
problems with various bits and pieces of gcc segfaulting.  In all those 
cases, going back to gmp-6.0.0a got things back to working.  Two problems 
have been observed on Broadwell CPU (i5-5300U and i7-5600U) and all on 64bit 
(x86_64).  Looking at the release notes the only thing that stands out is 
the ADX instruction support for Broadwell/Skylake, which incidentally isn't 
used in 32bit when a fat binary is built (at least my interpretation of 
fat.c is that Broadwell/Skylake have no special treatment for 32bit, which 
is a bit peculiar -- I'd think they should at least get listed along with 
Haswell).  I can't test on either architecture myself.

Since I don't want to downrev gmp for everybody, is there an easy way to 
skip that bit of code when building gmp?  That would also provide an 
indication of whether that is the right spot to further investigate where 
the problems in the applications come from.

Thank you.


Regards,
Achim.
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