Fix PR16651, an assert introduced in my recent re-work of the innards of
SROA.

The crux of the issue is that now we track uses of a partition of the
alloca in two places: the iterators over the partitioning uses and the
previously collected split uses vector. We weren't accounting for the
fact that the split uses might invalidate integer widening in ways other
than due to their width (in this case due to being volatile).

Further reduced testcase added to the tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186655 91177308-0d34-0410-b5e6-96231b3b80d8
A long overdue cleanup in SROA to use 'DL' instead of 'TD' for the
DataLayout variables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186656 91177308-0d34-0410-b5e6-96231b3b80d8
Fix uninitialized memory read found by MemorySanitizer: always set output parameter of ConvergingScheduler::SchedBoundary::getOtherResourceCount

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186658 91177308-0d34-0410-b5e6-96231b3b80d8
Try to move to a more reasonable set of naming conventions given the new
implementation of the SROA algorithm. We were using the term 'partition'
in many places that no longer ever represented an actual partition, but
rather just an arbitrary slice of an alloca.

No functionality change intended here. Mostly just renaming of types,
functions, variables, and rewording of comments. Several comments were
rewritten to make a lot more sense in the new structure of things.

The stats are still weird and not reflective of how this really works.
I'll fix those up in a separate patch as it is a touch more semantic of
a change...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186659 91177308-0d34-0410-b5e6-96231b3b80d8