Error related to GCC LTO optimization for GMP at ARM AArch64

[Some One]

Dear GMP devs,

As I reported the same issue to gentoo bugzilla and retried to reproduce
for them with all logs attached,
I've found out that iproute2 magically started to compile OK.

However, there were other sources whose compilation was broken.

Another example with all previous flags for GMP:

1. git clone https://github.com/cjlin1/liblinear.git
2. cd liblinear/ && make:
c++ -Wall -Wconversion -O3 -fPIC -c -o newton.o newton.cpp
... hangs on the first source ...

Regards






пт, 6 янв. 2023 г. в 17:03, Some One <gluker at gmail.com>:

> Hi,
>
> Let me try to reproduce the whole process with original GMP source:
>
> 1. I've downloaded https://gmplib.org/download/gmp/gmp-6.2.1.tar.xz
>
> 2. Exported my CFLAGS with LTO enabled:
> export COMMON_FLAGS="-O3 -march=native -mcpu=native -pipe -funroll-loops \
>     -fomit-frame-pointer -fforce-addr -ftracer -fno-stack-protector -flto"
> export CFLAGS="${COMMON_FLAGS}"
> export CXXFLAGS="${COMMON_FLAGS}"
>
> 3. Configure, make & install GMP with gcc version 12.2.1 20221231:
> ./configure --prefix=/usr/ --libdir=/usr/lib64/ --enable-cxx
> make -j4
> make install
>
> 4. Cloned iproute2:
> git clone git://git.kernel.org/pub/scm/network/iproute2/iproute2.git
>
> 5. Try to compile iproute2 with hang as follows:
>     CC       tc_cbq.o
>     CC       tc_estimator.o
>     ... hangs here ...
>
> 6. Commented out the following piece of iproute2 code in tc/tc_estimator.c:
>            // if (A/(-log(w)) > time_const)
>            //      break;
>
> 7. Continued to compile iproute2 and compilation went OK
>
> Same error was reproduced with current https://gmplib.org/repo/gmp-6.2/
>
> Switching off LTO let iproute2 compile OK
>
> Regards!
>
> пт, 6 янв. 2023 г. в 15:00, Torbjörn Granlund <tg at gmplib.org>:
>
>> Some One <gluker at gmail.com> writes:
>>
>>   I've found the problem related to GCC LTO optimization for GMP for ARM
>>   aarch64
>>   under QEMU with ARM Neoverse-N1 virt-4.2 (Oracle Cloud) and ARM virt-7.2
>>   (Apple M1)
>>   both running the latest Gentoo with gmp-6.2.1-r5 compiled by both
>>   gcc version 11.3.1 20221209 and gcc version 12.2.1 20221231.
>>
>>   To reproduce:
>>   1. Compile GMP with LTO optimization -- compiles OK
>>   2. Try to compile iproute2-6.1.0 or cmake-3.25.1 -- compilation hangs
>>   during the process
>>
>>   Disabling LTO optimization for GMP solves the problem.
>>
>> I would not expect any GMP developer to attempt to reproduce this
>> problem.  You're using a patched GMP ("-r5") in an environment which
>> would be very close to impossible to reproduce!
>>
>> You need to isolate this problem and only then report it to the package
>> maintainer of the buggy program.
>>
>> --
>> Torbjörn
>> Please encrypt, key id 0xC8601622
>>
>