Fix undefined behaviour sanitiser errors (avx2 + LHCbMath/Similarity)

I ran locally with the undefined behaviour sanitiser in an avx2-enabled build and saw a couple of errors, one alignment issue:

../Kernel/LHCbMath/src/Similarity.cpp:94:12: runtime error: load of misaligned address 0x7ffcee0396e8 for type '__m256d', which requires 32 byte alignment

and one out-of-range access

@sponce can you take a look? I'm not that familiar with Vc, maybe there is a better/nicer way to make explicit that these are unaligned loads?

cc: @jonrob

added backport run2 label

assigned to @mzdybal

/ci-test --merge

• [2020-08-27 17:22] Validation started with lhcb-master-mr#1222
• [2020-08-31 16:11] Validation started with lhcb-master-mr#1242

mentioned in issue Moore#205 (closed)

assigned to @vrenaudi and unassigned @mzdybal

ping @sponce -- can you have a quick look at this?

added 29 commits

• f5716bbe...282905a2 - 27 commits from branch master
• c8c7a751 - Fix ub sanitiser errors that appear in avx2 builds (LHCbMath/Similarity).
• 71164480 - Remove explicit _mm256_loadu_pd intrinsics.

Compare with previous version

@vrenaudi this is ready to be tested.

/ci-test --merge

mentioned in issue Moore#206 (closed)

assigned to @dcampora

assigned to @dovombru and unassigned @dcampora

added bug fix label

resolved all threads

approved this merge request

merged

mentioned in commit b6361be4

unassigned @vrenaudi and @dovombru