WebAssembly: don't optimize memcpy/memmove/memcpy to frame index

r258781 optimized memcpy/memmove/memcpy so the intrinsic call can return its first argument, but missed the frame index case. Teach it to ignore that case so C code doesn't assert out in these cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258851 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed