__BIGGEST_ALIGNMENT / more on arch compiler defines

[Toebs Douglass]

Hej, all.

I asked recently about the largest supported alignment.

Turns out there is a compiler defined define, "__BIGGEST_ALIGNMENT",
which indicates this value.  It is usually small (16 bytes kindafing).

It seems to have in older versions (something like 4.5 ish and earlier)
to have been named "BIGGEST_ALIGNMENT".

In other news, I've been experimenting again with the "__i686" define.

As far as I can tell, it is defined for arch "i686" up to and including
"pentium3" (I'm currently using 5.4.0).

https://gcc.gnu.org/onlinedocs/gcc-5.4.0/gcc/x86-Options.html#x86-Options

For my 32-bit atom processor, which has SSE3, I was trying to use
"prescott" - but having done so, and looking at the compiler defines,
it's not apparent to me now I can know I'm on prescott, because what I
see in the compiler defines is "__nocona" which is I think much the same
but is 64-bit.