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/SIMachineFunctionInfo.cpp b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
index 1b74c14..7c5bc74 100644
--- a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
@@ -47,7 +47,7 @@
     ImplicitArgPtr(false),
     GITPtrHigh(0xffffffff),
     HighBitsOf32BitAddress(0) {
-  const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
+  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
   const Function &F = MF.getFunction();
   FlatWorkGroupSizes = ST.getFlatWorkGroupSizes(F);
   WavesPerEU = ST.getWavesPerEU(F);
@@ -178,7 +178,7 @@
 
 void SIMachineFunctionInfo::limitOccupancy(const MachineFunction &MF) {
   limitOccupancy(getMaxWavesPerEU());
-  const SISubtarget& ST = MF.getSubtarget<SISubtarget>();
+  const GCNSubtarget& ST = MF.getSubtarget<GCNSubtarget>();
   limitOccupancy(ST.getOccupancyWithLocalMemSize(getLDSSize(),
                  MF.getFunction()));
 }
@@ -253,7 +253,7 @@
   if (!SpillLanes.empty())
     return true;
 
-  const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
+  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
   const SIRegisterInfo *TRI = ST.getRegisterInfo();
   MachineFrameInfo &FrameInfo = MF.getFrameInfo();
   MachineRegisterInfo &MRI = MF.getRegInfo();