is there a way to do _umul128 on posix ?

[a11e99z]

On Tuesday, 10 September 2019 at 04:13:25 UTC, Newbie2019 wrote:
> I need _umul128 to do the fast math,   is there a way to made 
> it work for posix ?
>
> On windows I can use _umul128, is there a ASM or work around in 
> LDC to do this on posix ?

https://run.dlang.io/is/2xYt5j

struct m128 { ulong lo, hi; }

// REX.W + F7 /4 	MUL r/m64 	(RDX:RAX ← RAX ∗ r/m64).
// 
https://en.wikipedia.org/wiki/X86_calling_conventions#x86-64_calling_conventions
// Windows RCX, RDX, R8, R9. returns RAX only
// Linux RDI, RSI, RDX, RCX, R8, R9. returns RDX:RAX
m128 mul128( ulong a, ulong b ) pure nothrow @nogc @trusted {
     asm pure @nogc nothrow {
	naked;
	mov RAX, RDI;
         mul RSI;
         ret;
     }
}
// probably u can do it inline