Re: is Vax addressing sane today

Terje Mathisen <terje.mathisen@tmsw.no> writes:

Tim Rentsch wrote:

[...]

I am currently in the position of needing to take some code
written for Linux/Unix and get it running in MS Windows.
>
My attempts to use MSVC have been frustrating, because of some
limitations of that environment.  The two most prominent are
these:  long double is only 64 bits, and there are no integer
types of 128 bits that I could find.
>
Are there any MSVC folks here who can help with these problems?
I am not an MSVC expert by any means and easily could have missed
something.
>
I should mention that the code is written in C, not C++, and that
is not something I am at liberty to change.

>
I seem to remember finding something like __int128_t and __uint128_t
inside MSVC?

Apparently VScode has added or is going to add support for
the pre-defined type names __int128_t and __uint128_t.  That
is good to know even though it doesn't bear directly on my
question.

And that by casting uint64_t parameters to the u128 variant, the
compiler would generate the obvious MUL RDI and save RDX:RAX as the
128-bit result:
>
uint128_t mulw(uint64_t a, uint64_t b)
{
  return (uint128_t) a * (uint128_t) b;
}
>
I.e. no subroutine call/zero overhead.
>
OTOH, getting optimal wide integer accumulators is a bit harder,
needing compiler intrinsics to access the widening add with carry
opcodes.  (ADDX)

This information doesn't affect what I am hoping to accomplish,
because any arithmetic on 128-bit types would already be held
in 128-bit values.  Thank you though for the information.