Benchmarks for i128 in wasm

Collecting data for https://github.com/WebAssembly/128-bit-arithmetic/

Running benchmarks

First install some dependencies:

Rust & Cargo
- run rustup target add wasm32-wasip1 for a compilation target
Wasmtime
Node.js & NPM
JSVU to get some JS runtimes

Then collect data for your native platform:

$ cargo run --release -- --bench --save-baseline native

Instructions below are how to build the benchmark program, a Rust binary, and
then compare the benchmark results in wasm to those that are collected above on
native. By default the wide-arithmetic proposal is disabled in Rust so the
instructions below collect baseline "wasm today" data. To collect data with wide
arithmetic use:

$ export CARGO_TARGET_WASM32_WASIP1_RUSTFLAGS=-Ctarget-feature=+wide-arithmetic

Set that before the cargo build or the cargo run command to pass the right
flags to the compiler to enable wide-arithmetic instructions.

Note that support for -Ctarget-feature=+wide-arithmetic is only in Rust 1.87.0
which is currently the Nightly Rust channel. That means you'll need to be using
a Nightly Rust compiler and rustc -vV should LLVM version 20.1.0. To run the
Nightly compiler you'll use cargo +nightly run ... or cargo +nightly build ..., basically add +nightly right after the cargo executable.

Wasmtime

$ export CARGO_TARGET_WASM32_WASIP1_RUNNER='wasmtime --dir .'
$ cargo run --release --target wasm32-wasip1 -- --bench --baseline native

Node.js

$ cargo build --release --target wasm32-wasip1
$ node run-node.js target/wasm32-wasip1/release/wasm-benchmark-i128.wasm --bench --baseline native

Browser

$ cargo build --release --target wasm32-wasip1
$ http

Each link at the top can be used to run the benchmark. Note that the formatting
is a bit weird

Spidermonkey

Use jsvu to get a spidermonkey executable then:

$ cargo build --release --target wasm32-wasip1
$ spidermonkey -m spidermonkey.js ./global.js \
    ./target/wasm32-wasip1/release/wasm-benchmark-i128.wasm \
    --bench --baseline native

V8

Use jsvu to get a v8 executable then:

$ cargo build --release --target wasm32-wasip1
$ v8 --module v8.js -- \
    ./target/wasm32-wasip1/release/wasm-benchmark-i128.wasm \
    --bench --baseline native

Note that this will "hang" for a moment without intermediate output as results
are generated.

JSC

Use jsvu to get a jsc executable then:

$ cargo build --release --target wasm32-wasip1
$ jsc -m jsc.js -- \
    ./target/wasm32-wasip1/release/wasm-benchmark-i128.wasm \
    --bench --baseline native

README