Successful build and some autotuning of GCC 7.1.0 on Raspberry Pi 3

[Grigori Fursin]

Dear GCC colleagues,

I managed to build GCC 7.1.0 on Raspberry Pi 3 (Raspbian GNU/Linux 8 
(jessie), GCC 4.9.2). It required combination of specific configuration 
flags:

--with-cpu=cortex-a53 --with-fpu=neon-fp-armv8 --with-float=hard 
--build=arm-linux-gnueabihf --host=arm-linux-gnueabihf 
--target=arm-linux-gnueabihf --disable-bootstrap

By the way, if it's of any interest, I also automated such customized 
builds using Collective Knowledge workflow framework:

$ sudo pip install ck
$ ck pull repo:ck-dev-compilers
$ ck install package:compiler-gcc-any-src-linux-no-deps 
--env.PARALLEL_BUILDS=1 --env.GCC_COMPILE_CFLAGS=-O0 
--env.GCC_COMPILE_CXXFLAGS=-O0 --env.EXTRA_CFG_GCC=--disable-bootstrap 
--env.RPI3=YES

This also allowed us to autotune GCC 7.1.0 across shared programs/data 
sets and collect some "interesting" combinations of optimization flags here:
* http://tinyurl.com/k4jlwq5

If you build GCC via CK as above, you are welcome to participate in 
collaborative optimization and share stats for your platforms/compiler 
as following:

$ ck crowdsource program.optimization --iterations=80 --repetitions=3 
--scenario=8289e0cf24346aa7ck

Cheers,
Grigori