tests: remove unused type aliases

Signed-off-by: Matthias Kretz <kretz@kde.org>
simdarray: add shifted member function

fully tested and functional in the range -2*Size+1 .. 2*Size-1

Signed-off-by: Matthias Kretz <kretz@kde.org>
utils test: fix mask cast by using simd_cast

Signed-off-by: Matthias Kretz <kretz@kde.org>
simd_cast: add debug trace output

since simd_cast implementations depend on relatively deep nesting of
simd_cast calls it is very helpful to trace the calls to understand
where something goes wrong. Thanks to variadic templates this is
non-trivial to do, therefore I developed a helper function that does the
trick and can be enabled via the VC_DEBUG_SIMD_CAST macro.

Signed-off-by: Matthias Kretz <kretz@kde.org>
simd_cast: fix implementation selection

The enable_if logic was slightly off and lead to important input values
getting dropped before the actual converting calls were made. Now the
logic should be correct and never drop necessary data.

Signed-off-by: Matthias Kretz <kretz@kde.org>
simd_cast: improve offset == 0 calls

with offset == 0 and some combination of To/From types the fallback
(scalar copy) implementation was used, even though simply dropping the
offset from the call would improve the implementation selection
strategy. This also fixes a bug in mask conversion. Though the bug is
still latent in the fallback conversion function.

Signed-off-by: Matthias Kretz <kretz@kde.org>
simd_cast more debug calls

three more simd_cast<offset> calls that didn't have a vc_debug_ call
yet.

Signed-off-by: Matthias Kretz <kretz@kde.org>