Changes

Changes from Git (git https://github.com/llvm/llvm-project.git)

Summary

  1. [DSE,MemorySSA] Add an early check for read clobbers to traversal. (details)
Commit efb8e156daa120a25f993b3142ef8d6ef766df5a by flo
[DSE,MemorySSA] Add an early check for read clobbers to traversal.

Depending on the benchmark, this early exit can save a substantial
amount of compile-time:

http://llvm-compile-time-tracker.com/compare.php?from=505f2d817aa8e07ba98e5fd4a8f6ff0666f89df1&to=eb4e441147f9b4b7a5fcbbc57428cadbe9e01f10&stat=instructions
The file was addedllvm/test/Transforms/DeadStoreElimination/MSSA/read-clobber-after-overwrite.ll
The file was modifiedllvm/lib/Transforms/Scalar/DeadStoreElimination.cpp