Merge r322325 from upstream. This allows devel/godot to build in a

reasionable abount of time:

PeepholeOpt cleanup/refactor; NFC

- Less unnecessary use of `auto`
- Add early `using RegSubRegPair(AndIdx) =` to avoid countless
  `TargetInstrInfo::` qualifications.
- Use references instead of pointers where possible.
- Remove unused parameters.
- Rewrite the CopyRewriter class hierarchy:
   - Pull out uncoalescable copy rewriting functionality into
     PeepholeOptimizer class.
   - Use an abstract base class to make it clear that rewriters are
     independent.
- Remove unnecessary \brief in doxygen comments.
- Remove unused constructor and method from ValueTracker.
- Replace UseAdvancedTracking of ValueTracker with DisableAdvCopyOpt use.

PR:		228261
Reported by:	FreeBSD@ShaneWare.Biz

devel/llvm60/Makefile

@@ -2,7 +2,7 @@
 
 PORTNAME=	llvm
 DISTVERSION=	6.0.0
-PORTREVISION=	3
+PORTREVISION=	4
 CATEGORIES=	devel lang
 MASTER_SITES=	http://${PRE_}releases.llvm.org/${LLVM_RELEASE}/${RCDIR}
 PKGNAMESUFFIX=	${LLVM_SUFFIX}