DebugInfo: Ensure that all debug location scope chains from instructions within a function, lead to the function itself.

Originally committed in r211723, reverted in r211724 due to failure
cases found and fixed (ArgumentPromotion: r211872, Inlining: r212065),
and I now believe the invariant actually holds for some reasonable
amount of code (but I'll keep an eye on the buildbots and see what
happens... ).

Original commit message:

PR20038: DebugInfo: Inlined call sites where the caller has debug info
but the call itself has no debug location.

This situation does bad things when inlined, so I've fixed Clang not to
produce inlinable call sites without locations when the caller has debug
info (in the one case where I could find that this occurred). This
updates the PR20038 test case to be what clang now produces, and readds
the assertion that had to be removed due to this bug.

I've also beefed up the debug info verifier to help diagnose these
issues in the future, and I hope to add checks to the inliner to just
assert-fail if it encounters this situation. If, in the future, we
decide we have to cope with this situation, the right thing to do is
probably to just remove all the DebugLocs from the inlined instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212085 91177308-0d34-0410-b5e6-96231b3b80d8
ExecutionEngine::create(): fix interpreter fallback when JIT is unavailable

ForceInterpreter=false shouldn't disable the interpreter completely because it
can still be necessary to interpret if the target doesn't support JIT.

No obvious way to test this in LLVM, but this matches what
LLVMCreateExecutionEngineForModule() does and fixes the clang-interpreter
example in the clang source tree which uses the ExecutionEngine.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212086 91177308-0d34-0410-b5e6-96231b3b80d8
MachineScheduler: better book-keeping for asserts.

Fixes another test case under PR20057.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212088 91177308-0d34-0410-b5e6-96231b3b80d8