Run benchmarks with binaryen/wabt/wavm and potentially in browsers

[lrettig]

[lrettig]

@poemm began looking into this (although I don't think he's actually run any benchmarks yet). Per his update today:

• Firefox advertises one pass wasm to native binary
• Looked into Chakra (Microsoft’s engine), Webkits (Apple), V8 (Google), Spidermonkey (Firefox)
• I believe Firefox is the best one
• webkit has something close but has intermediate representation
• Chakra does something very complicated
• V8 has some directed graph based intermediate representation, loops correspond cycles in graph, many nested loops lead to a big slowdown
• I read the Firefox source code, there’s a file https://dxr.mozilla.org/mozilla-central/source/js/src/wasm/WasmBaselineCompile.cpp, would be great if we can get it to run standalone, they advertise a single pass to binary which is exactly what we need
• this isn’t testnet critical but useful for later
• Casey: Guido thought there is a pretty simple patch for WAVM to make it bomb proof
• WAVM might be another good way forward; it’s what we’re using for Hera
• WAVM does use intermediate rep., for testing that’s fine but for production we may want something faster