cmake change for correct placement of autodetected tune & arch flags of GCC and SVE enablement on AARCH64

[abondarev84]

also updated README for SVE short explanation

[markos]

Unfortunately, this fails on all other platforms currently on our Jenkins CI:

https://jenkins.vectorcamp.gr/blue/organizations/jenkins/VectorCamp%2Fvectorscan-ci/detail/vectorscan-ci/109/pipeline (direct URLs fail for Blue Ocean plugin).

If this is to be accepted it has to continue working for all other architectures.

[markos]

@abondarev84 By the way, when you are done, could you please submit this PR against develop branch? Thanks.

[abondarev84]

of course

[markos]

I confirm that it works on my graviton3 system with gcc, unfortunately it fails with clang (tested 11 and 13).

[abondarev84]

I confirm that it works on my graviton3 system with gcc, unfortunately it fails with clang (tested 11 and 13).

do you mind referencing to what failed? run jenking run 124 is still running without errors so far.

for run 123 I see that sve wasn't found but it wasn't in the flags or cmake command.

[markos]

Jenkins jobs do not run SVE specific builds (yet), it's only NEON. If you try building on graviton3 system with
CC=clang CXX=clang++ cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SVE=on ..

you will see the error.

[abondarev84]

Jenkins jobs do not run SVE specific builds (yet), it's only NEON. If you try building on graviton3 system with CC=clang CXX=clang++ cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SVE=on ..

you will see the error.

there were no changes to clang logic path.
what I'm seeing as the cause here is that the error of not having arm_sve.h happens for lack of a file identification in the includes.
I can update the commit message to reflect that these fixes were implemented for gcc.

[markos]

The problem is that it has to work for clang as well, before it can be merged. I see that clang correctly sets -march=armv8+sve in the CFLAGS/CXXFLAGS, so I'm wondering why it fails to detect arm_sve.h.

[markos]

right, ARCH_C_FLAGS/ARCH_CXX_FLAGS are set correctly, but they are not used in CHECK_INCLUDE_FILE_CXX for clang, which leads to failure.

[markos]

yup, that's it, adding this line before the CHECK_INCLUDE_FILE_CXX, line 361, fixes the build:
set(CMAKE_REQUIRED_FLAGS ${ARCH_CXX_FLAGS})

[markos]

could you also remove Jenkinsfile from the PR? thanks

[abondarev84]

could you also remove Jenkinsfile from the PR? thanks

I updated my fork, should I remove the merge from remote and leave my repo at my newest commit?
(I can't just remove the file from the pr in githubs ui it seems)

[abondarev84]

@markos removed the merge from your origin.

[markos]

ok, let's fix the clang issue as mentioned in #125 (comment) and wait for jenkins to be done and it should be good to go :)