Sanitize MCJIT remote execution

MCJIT remote execution (ChildTarget+RemoteTargetExternal) protocol was in
dire need of refactoring. It was fail-prone, had no error reporting and
implemented the same message logic on every single function.

This patch rectifies it, and makes it work on ARM, where it was randomly
failing. Other architectures shall profit from this change as well, making
their buildbots and releases more reliable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199261 91177308-0d34-0410-b5e6-96231b3b80d8
Re-enable remote MCJIT tests on ARMv7

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199262 91177308-0d34-0410-b5e6-96231b3b80d8
Enable use of ranges for translation units in the presence of
-ffunction-sections and update comments and TODOs about other
places that we should enable this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199263 91177308-0d34-0410-b5e6-96231b3b80d8
Add the lld root to llvm-lit, so llvm-lit can be used
to run lld tests individually.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199264 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: don't try to handle [SU]MUL_LOHI nodes

We should set them to expand for now since there are no patterns
dealing with them. Actually, there are no instructions either so I
doubt they'll ever be acceptable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199265 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: correctly determine final tBX_LR in Thumb1 functions

The changes caused by folding an sp-adjustment into a "pop" previously
disrupted the forward search for the final real instruction in a
terminating block. This switches to a backward search (skipping debug
instrs).

This fixes PR18399.

Patch by Zhaoshi.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199266 91177308-0d34-0410-b5e6-96231b3b80d8