[SROA] Update the documentation and names for accessing the slices
within a partition of an alloca in SROA.

This reflects the fact that the organization of the slices isn't really
ideal for analysis, but is the naive way in which the slices are
available while we're processing them in the core partitioning
algorithm.

It is possible we could improve matters, and I've left a FIXME with
one of my ideas for how to do this, but it is a lot of work, the benefit
is somewhat minor, and it isn't clear that it would be strictly better.
=/ Not really satisfying, but I'm out of really good ideas.

This also improves one place where the debug logging failed to mark some
split partitions. Now we log in one place, slightly later, and with
accurate information about whether the slice is split by the partition
being rewritten.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224800 91177308-0d34-0410-b5e6-96231b3b80d8
[OCaml] Expose Llvm_executionengine.get_{global_value,function}_address.

Patch by Ramkumar Ramachandra <artagnon@gmail.com>.

Also remove Llvm_executionengine.get_pointer_to_global, as it
is actually deprecated and didn't appear in a stable release.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224801 91177308-0d34-0410-b5e6-96231b3b80d8
[OCaml] PR21901: Update tests.

This finishes the fix partially applied by r224782.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224802 91177308-0d34-0410-b5e6-96231b3b80d8
LiveIntervalAnalysis: Fix performance bug that I introduced in r224663.

Without a reference the code did not remember when moving the iterators
of the subranges/registerunit ranges forward and instead would scan from
the beginning again at the next position.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224803 91177308-0d34-0410-b5e6-96231b3b80d8
LiveRangeEdit: Check for completely empy subranges after removing ValNos.

Completely empty subranges are not allowed and must be removed when
subreg liveness is enabled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224804 91177308-0d34-0410-b5e6-96231b3b80d8
RegisterCoalescer: With subrange liveness there may be no RedefVNI for unused lanes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224805 91177308-0d34-0410-b5e6-96231b3b80d8
LiveInterval: Introduce createMainRangeFromSubranges().

This function constructs the main liverange by merging all subranges if
subregister liveness tracking is available. This should be slightly
faster to compute instead of performing the liveness calculation again
for the main range. More importantly it avoids cases where the main
liverange would cover positions where no subrange was live. These cases
happened for partial definitions where the actual defined part was dead
and only the undefined parts used later.

The register coalescing requires that every part covered by the main
live range has at least one subrange live.

I also expect this function to become usefull later for places where the
subranges are modified in a way that it is hard to correctly fix the
main liverange in the machine scheduler, we can simply reconstruct it
from subranges then.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224806 91177308-0d34-0410-b5e6-96231b3b80d8