AMDGPU: Refactor Subtarget classes

Summary:
This is a follow-up to r335942.
- Merge SISubtarget into AMDGPUSubtarget and rename to GCNSubtarget
- Rename AMDGPUCommonSubtarget to AMDGPUSubtarget
- Merge R600Subtarget::Generation and GCNSubtarget::Generation into
  AMDGPUSubtarget::Generation.

Reviewers: arsenm, jvesely

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D49037

llvm-svn: 336851
diff --git a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
index 913e22e..d456e3d 100644
--- a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
@@ -136,7 +136,7 @@
 // "s_waitcnt 0" before use.
 class BlockWaitcntBrackets {
 public:
-  BlockWaitcntBrackets(const SISubtarget *SubTarget) : ST(SubTarget) {
+  BlockWaitcntBrackets(const GCNSubtarget *SubTarget) : ST(SubTarget) {
     for (enum InstCounterType T = VM_CNT; T < NUM_INST_CNTS;
          T = (enum InstCounterType)(T + 1)) {
       memset(VgprScores[T], 0, sizeof(VgprScores[T]));
@@ -314,7 +314,7 @@
   void dump() { print(dbgs()); }
 
 private:
-  const SISubtarget *ST = nullptr;
+  const GCNSubtarget *ST = nullptr;
   bool WaitAtBeginning = false;
   bool RevisitLoop = false;
   bool MixedExpTypes = false;
@@ -364,7 +364,7 @@
 
 class SIInsertWaitcnts : public MachineFunctionPass {
 private:
-  const SISubtarget *ST = nullptr;
+  const GCNSubtarget *ST = nullptr;
   const SIInstrInfo *TII = nullptr;
   const SIRegisterInfo *TRI = nullptr;
   const MachineRegisterInfo *MRI = nullptr;
@@ -1837,7 +1837,7 @@
 }
 
 bool SIInsertWaitcnts::runOnMachineFunction(MachineFunction &MF) {
-  ST = &MF.getSubtarget<SISubtarget>();
+  ST = &MF.getSubtarget<GCNSubtarget>();
   TII = ST->getInstrInfo();
   TRI = &TII->getRegisterInfo();
   MRI = &MF.getRegInfo();