Recommitting Craig Topper's patch now that r296476 has been recommitted.

Recommitting Craig Topper's patch now that r296476 has been recommitted.

When checking if chain node is foldable, make sure the intermediate nodes have a single use across all results not just the result that was used to reach the chain node.

This recovers a test case that was severely broken by r296476, my making sure we don't create ADD/ADC that loads and stores when there is also a flag dependency.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297698 91177308-0d34-0410-b5e6-96231b3b80d8