Revert r186316 while I track down an ASan failure and an assert from
a bot.

This reverts the commit which introduced a new implementation of the
fancy SROA pass designed to reduce its overhead. I'll skip the huge
commit log here, refer to r186316 if you're looking for how this all
works and why it works that way.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186332 91177308-0d34-0410-b5e6-96231b3b80d8
Remove trailing whitespace


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186333 91177308-0d34-0410-b5e6-96231b3b80d8
Remove invalid assert in DAGTypeLegalizer::RemapValue

There is a comment at the top of DAGTypeLegalizer::PerformExpensiveChecks
which, in part, says:

  // Note that these invariants may not hold momentarily when processing a node:
  // the node being processed may be put in a map before being marked Processed.

Unfortunately, this assert would be valid only if the above-mentioned invariant
held unconditionally. This was causing llc to assert when, in fact,
everything was fine.

Thanks to Richard Sandiford for investigating this issue!

Fixes PR16562.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186338 91177308-0d34-0410-b5e6-96231b3b80d8