Am 16.01.20 um 23:22 schrieb J. Gareth Moreton:
Hey everyone,
Maybe I'm being a bit pedantic with this, but must we abide by C/C++
standards and go by the name __m128 etc. for the 128-bit data type?
They can be added additionally. After some thinking, I came to the
conclusion we should first go with the same naming C uses (as we do in
every library header meanwhile), on top of this some more pascalish way
can be added.
Being as how Pascal tended to go for more readable and BASIC-inspired
names like Integer and Single, might it be better to name them TM128
instead? If not that, then is it possible to add a union-like record
type to the System unit or the inc files that contain all of the
intrinsics?
The point is: only these types enable the compiler to use the right mov
instructions. Using a record means there is no rule which mov
instructions (movdqa, movabs, movapd etc.) should be used.
My vectorcall tests (e.g. tests\test\cg\tvectorcall1.pp) have something
like this:
{$PUSH}
{$CODEALIGN RECORDMIN=16}
{$PACKRECORDS C}
type
TM128 = record
case Byte of
0: (M128_F32: array[0..3] of Single);
1: (M128_F64: array[0..1] of Double);
end;
{$POP}
Granted, given that __m128 will be automatically aligned, all of the
codealign directives may not be necessary - for example:
type
TM128 = record
case Byte of
0: (M128_F32: array[0..3] of Single);
2: (M128_F64: array[0..1] of Double);
3: (M128_Internal: __m128);
end;
The main thing I'm thinking about is that it's actually rather difficult
to modify the elements of a variable of type __m128 directly in C/C++
because of the type being opaque and difficult to typecast sometimes
(some compilers will treat it as an array, others will treat it as a
record type like the above (Visual C++ does this), while others may not
allow access to its elements at all). Often, I might want to map a
4-component vector with Single-type fields x, y, z and w to an aligned
__m128 type, or Double-type fields Re and Im when dealing with complex
numbers. That way, I can read from and write to them outside of
intrinsic calls.
I suppose I'm suggesting we introduce something more usable than what C
has so people can actually use intrinsics more easily.
Gareth aka. Kit
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