AVX types: __m256d versus __v4sd

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I noticed that the AVX vector of 4 double has 2 names, __v4sd and __m256d (actually we have the same duality for SSE), and I'd like to know when I should use which name.

The only difference is the may_alias attribute. I expect that casting a __v4sd* to a double* doesn't require the may_alias attribute, and that problems only start if I try casting a __v4sd* to a __v4di*?

On the other hand, Intel only documents __m256d (the may_alias version), so portability says to use that one.

Marc Glisse

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