Extending integer arithmetic support in WASM

[eisenwave]

I would like to propose for WebAssembly that the integer arithmetic support be extended in future versions. I've noticed that over the years, a fair amount of issues here labeled integer have been created, but there doesn't appear to be any active proposal for resolving these:

• https://github.com/WebAssembly/design/issues?q=is%3Aissue%20state%3Aopen%20label%3Ainteger

Some possible candidates:

• i32.mulh and i64.mulh for obtaining the high bits of a 64-bit multiplication (64-bit Widening Multiplication #1495)
• i32.clmul, i64.clmul, i32.clmulh, and i64.clmulh for obtaining the low and high bits of a carry-less multiplication (corresponding to @llvm.clmul) (New insn: Carry-less multiply (CLMUL) #1388)
• i32.pext, i64.pext, i32.pdep, and i64.pdep for parallel bit extract / parallel bit deposit, corresponding to @llvm.pext and @llvm.pdep (Accelerated bitfield instructions: PDEP, PEXT and BEXTR? #1389)
• i32.rbit and i64.rbit for reversing the bits in an integer corresponding to the rbit ARM instruction (Bit reversing instructions #1382)

It is very unfortunate when you incur a significant performance cost when targeting WASM because these instructions are not available. For example, you can use the C++29 std::bit_compress function (which I've personally gotten into the standard by the way) to portable spell a PEXT operation, but this would get expanded to so many WASM instructions that you probably couldn't reconstruct pext in the JIT compiler on the other end because the expansion is way too complex.

Anyway, how do I get the ball rolling on this? I've joined the W3C Community Group. I am under the impression that if I don't champion this myself, it's not going to happen anytime soon.

Update: It has come to my attention that at least widening addition, subtraction, and multiplication are covered by https://github.com/WebAssembly/wide-arithmetic (phase 3)