[WebAssembly] Add experimental multivalue calling ABI

Authored by tlively on Jan 17 2020, 6:28 PM.


[WebAssembly] Add experimental multivalue calling ABI

For now, this ABI simply expands all possible aggregate arguments and
returns all possible aggregates directly. This ABI will change rapidly
as we prototype and benchmark a new ABI that takes advantage of
multivalue return and possibly other changes from the MVP ABI.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, sunfish, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D72972