Revert "[X86] Fix a variable name for r237977 so that it works with every compilers."

Revert "[X86] Fix a variable name for r237977 so that it works with every compilers."
Revert "[X86] Refactor the prologue emission to prepare for shrink-wrapping."

This reverts commit 6b3b93fc8b68a2c806aa992ee4bd3d7f61898d4b.
This reverts commit ab0b15dff8539826283a59c2dd700a18a9680e0f.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238011 91177308-0d34-0410-b5e6-96231b3b80d8