I personally would have thought the compiler would be smart enough to
promote a 128-bit array to an XMM register when among intrinstics or
just passing the structure as a whole from one place to another, but
utilise memory movement or the scalar SSE commands when modifying
individual fields. I guess it's easier said than done though and
probably something for me to research later on.
At the very least though, there should be a way to cleanly align a
structure to a 16-byte granularity in memory, since many of the SSE
instructions require this. I don't consider pre-processor directives to
be particularly clean and easy to use. True, one can use the "Move"
instruction to move data from your customised structure to an __m128,
and back again when you're finished, but this feels like an unnecessary
degree of overhead.
Gareth aka. Kit
On 18/01/2020 18:17, Florian Klämpfl wrote:
Am 18.01.20 um 18:52 schrieb J. Gareth Moreton:
I think more than anything I would like to see a degree of "ease of
use" for the SIMD intrinsics, since modifying __m128 data in C/C++ is
not that straightforward.
... because there exist in general no instructions to do so, e.g. you
cannot access a xmm register indexed with sse. Those intrinsics
provide only what the CPU can do directly.
Just as a straightforward example, what might be the best way to
ensure these following record types are compatible with the __m128
data types?
*type *TVector4 = *record*
X, Y, Z, W: Single;
*end*; // compatible with __m128f
*type *TComplex = *record*
Re, Im: Double;
*end*; // compatible with __m128d
Programmers on their own projects, whether it be a game or a
mathematical program, would much rather work with those constructs if
it can be helped... or at least I would.
This is another level of abstraction, the intrinsics aim really at a
direct usage of the sse/avx instructions. No more, no less.
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