[WebAssembly] WebAssemblyFastISel getelementptr variable index support

Summary:
Previously -fast-isel getelementptr would constant-fold non-constant i8
load/stores.

Reviewers: sunfish

Subscribers: jfb, dschuff, sbc100, llvm-commits

Differential Revision: https://reviews.llvm.org/D34044

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306060 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed