replace MachineCombinerPattern namespace and enum with enum class; NFCI

Also, remove an enum hack where enum values were used as indexes into an array.

We may want to make this a real class to allow pattern-based queries/customization (D13417).

llvm-svn: 252196
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index ae1b07b..51c85f6 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -230,7 +230,7 @@
 
 bool PPCInstrInfo::getMachineCombinerPatterns(
     MachineInstr &Root,
-    SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
+    SmallVectorImpl<MachineCombinerPattern> &Patterns) const {
   // Using the machine combiner in this way is potentially expensive, so
   // restrict to when aggressive optimizations are desired.
   if (Subtarget.getTargetMachine().getOptLevel() != CodeGenOpt::Aggressive)