CPU instruction sets do account for signed vs unsigned integers. SHR vs SAR for example. It's part of the ISAs. I'm calling this out as AFAIK, the JVM has no support for unsigned ints and so that in turn makes WASM a little more compelling.
Yes some instructions do - but surprisingly few (for instance there's signed/unsigned mul/div instructions, but add/sub are 'sign-agnostic'). The important part is that any 'signedness' is associated with the operation, and not with the operands or results.
Well, it has compiler intrinsics for unsigned numbers, for what it’s worth.