Compiling for ARMv8-A Using GCC 7.2.0 - Assertion error in gen-fac
Stephen_Damm at mentor.com
Fri Dec 6 15:29:46 UTC 2019
I also see no reasonable way for it to end up as 1. If I printf("%lu") those same two variables the results are even more strange:
== GCC 4.8.5 ==
== GCC 7.2.0 ==
So it appears like the "-1" being applies to GMP_HLIMB_BIT is a +1 in GCC 7.2.0. I've not encountered behaviour like this before. Very strange.
I am currently investigating if this is an issue with how GCC handles longs between 4.8.5 and 7.2.0 in ARM64 hosts builds.
This concludes me to believe a bug in GCC ARM64 or a bug in GMP or I am somehow building GCC wrong but right enough that it can compile most other libraries.
I do notice in GCC 4.8.5 -mabi is not specified when compiling GMP. When GCC 7.2.0 goes to build GMP it is being explicit about the -mabi=lp64.
If anything comes to mind let me know. I'll post back here if I find out the cause.
From: Niels Möller [mailto:nisse at lysator.liu.se]
Sent: December 6, 2019 03:51
To: Damm, Stephen <Stephen_Damm at mentor.com>
Cc: gmp-bugs at gmplib.org
Subject: Re: Compiling for ARMv8-A Using GCC 7.2.0 - Assertion error in gen-fac
"Damm, Stephen" <Stephen_Damm at mentor.com> writes:
> I was able to narrow down the cause. In GC 7.2.0 the GMP_LLIMB_MASK is wrong:
> =GCC 4.8.5=
> =GCC 7.2.0=
> From my understanding this might be a difference in how GCC 7.2.0 handles unsigned longs vs GCC 4.8.5. It also could be I am missing some vital compiler flag for GMP.
Can you file a gcc bug? These constants are defined as
#define GMP_LIMB_BITS (sizeof(mp_limb_t) * CHAR_BIT) /* 64, you say */
#define GMP_HLIMB_BIT ((mp_limb_t) 1 << (GMP_LIMB_BITS / 2)) #define GMP_LLIMB_MASK (GMP_HLIMB_BIT - 1)
I see no reasonable way that can end up defining GMP_LLIMB_MASK as 1.
Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
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