Don't pass the cpu flags detected by Vc to the compiler

Vc detects CPU flags based on the name of the CPU. This can be a problem in virtualization environment, when the name of the CPU is visible, but not all features are enabled in the guest.

Also, enabling all detected features in the the compiler makes it difficult to impossible for the user to force his own feature flags, e.g. to cross-build generic executables on hosts with many features to be run later on hosts with fewer features.

Closes: docker/ci#9

WIP:

• properly test, in particular in the light of docker/ci!46 (merged) being applied to the ci images
• ansgar proposed getting rid of all the Vc_COMPILE_FLAGS, too. Try that: !679 (closed) (redifined !679 (closed) as an add-on to this one, so it does not stop me from merging this one)
• changelog entry (deferred to #163 (closed))

changed the description

mentioned in issue docker/ci#9

Here is a test: build.sh

• Built docker images using the above script on sky (avx512)
• Transfered the images to epic (avx2)
• run them on epic
  • the master image fails with sigill or similar
  • the avoid-vc-cpu-detection image succeeds

marked the checklist item properly test, in particular in the light of docker/ci!46 (merged) being applied to the ci images as completed

mentioned in merge request !679 (closed)

changed the description

The downside of this is that now a long-gone warning reappears:

In file included from /ci/src/dune-common/dune/common/simd/simd.hh:11,
                 from /ci/src/dune-common/dune/common/densematrix.hh:20,
                 from /ci/src/dune-common/dune/common/fmatrix.hh:15,
                 from /ci/src/dune-common/dune/common/test/fmatrixtest.cc:19:
/ci/src/dune-common/dune/common/simd/interface.hh: In function 'bool Dune::Simd::allTrue(Mask) [with Mask = Vc_1::SimdMaskArray<double, 8, Vc_1::Vector<double, Vc_1::VectorAbi::Sse>, 2>]':
/ci/src/dune-common/dune/common/simd/interface.hh:437:10: note: The ABI for passing parameters with 64-byte alignment has changed in GCC 4.6
     bool allTrue(Mask mask)
          ^~~~~~~

Last time I fixed that note by changing the parameters from pass by value to const-ref: !607 (merged)

mentioned in issue #163 (closed)

changed the description

unmarked as a Work In Progress

merged

mentioned in commit 19557065

mentioned in issue #164 (closed)

mentioned in issue #165 (closed)