[x86] Hoist the actual lowering logic into a helper function to separate
it from the shuffle pattern matching logic.

Also cleaned up variable names, comments, etc. No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218152 91177308-0d34-0410-b5e6-96231b3b80d8
Converting the JITDebugLock mutex to a ManagedStatic to avoid the static constructor and destructor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218154 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Hoist a function up to the rest of the non-type-specific lowering
helpers, and re-flow the logic to use early exit and be a bit more
readable.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218155 91177308-0d34-0410-b5e6-96231b3b80d8
Converting object's error_category to a ManagedStatic to avoid static constructors and destructors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218160 91177308-0d34-0410-b5e6-96231b3b80d8