Emulate 64-bit mulh instruction

[Johan Engelen]

On Wednesday, 13 March 2019 at 16:06:34 UTC, Kagamin wrote:
> Apparently this has no intrinsic, so wrote this code for x86 to 
> compute 128 bit product:
> ...
> but the compiler doesn't recognize it as multiplication and 
> doesn't generate single imul instruction. Is the code wrong or 
> the compiler can't recognize it?

I think the compiler can't recognize it, judging from other posts 
online.

-Johan