Move getCommonSubClass() into TRI.

It will soon need the context.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140896 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveStackAnalysis.h

@@ -25,6 +25,8 @@
 namespace llvm {
 
   class LiveStacks : public MachineFunctionPass {
+    const TargetRegisterInfo *TRI;
+
     /// Special pool allocator for VNInfo's (LiveInterval val#).
     ///
     VNInfo::Allocator VNInfoAllocator;

include/llvm/CodeGen/MachineRegisterInfo.h

@@ -25,6 +25,8 @@ namespace llvm {
 /// registers, including vreg register classes, use/def chains for registers,
 /// etc.
 class MachineRegisterInfo {
+  const TargetRegisterInfo *const TRI;
+
   /// IsSSA - True when the machine function is in SSA form and virtual
   /// registers have a single def.
   bool IsSSA;