Merge #934

934: In LLVM backend, track which floats are guaranteed to be arithmetic, which makes the canonicalization a no-op. r=nlewycky a=nlewycky

# Description
This is a reimplementation of the patch in PR #651.

Extend state.rs ExtraInfo to track more information about floats. In addition to tracking whether the value has a pending canonicalization of NaNs, also track whether the value is known to be arithmetic (which includes infinities, regular values, and non-signalling NaNs (aka. "arithmetic NaNs" in the webassembly spec)). When the value is arithmetic, the correct sequence of operations to canonicalize the value is a no-op. Therefore, we create a lattice where pending+arithmetic=arithmetic.

Also, this extends the tracking to track all values, including non-SIMD integers. That's why there are more places where pending canonicalizations are applied.

Looking at c-wasm-simd128-example, this provides no performance change to the non-SIMD case (takes 58s on my noisy dev machine). The SIMD case drops from 46s to 29s.

# Review

- [ ] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Nick Lewycky <nick@wasmer.io>

CHANGELOG.md

@@ -13,6 +13,7 @@
 - [#990](https://github.com/wasmerio/wasmer/pull/990) Default wasmer CLI to `run`.  Wasmer will now attempt to parse unrecognized command line options as if they were applied to the run command: `wasmer mywasm.wasm --dir=.` now works!
 - [#987](https://github.com/wasmerio/wasmer/pull/987) Fix `runtime-c-api` header files when compiled by gnuc.
 - [#957](https://github.com/wasmerio/wasmer/pull/957) Change the meaning of `wasmer_wasi::is_wasi_module` to detect any type of WASI module, add support for new wasi snapshot_preview1
+- [#934](https://github.com/wasmerio/wasmer/pull/934) Simplify float expressions in the LLVM backend.
 
 ## 0.10.2 - 2019-11-18