[WebAssembly] Support frame pointer

Add support for frame pointer use in prolog/epilog.
Supports dynamic allocas but not yet over-aligned locals.
Target-independend CG generates SP updates, but we still need to write
back the SP value to memory when necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259220 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed