[AMDGPU] Removed dead SIMachineFunctionInfo::getWorkItemIDVGPR()

lib/Target/AMDGPU/SIMachineFunctionInfo.h

case 1:
       return ArgInfo.WorkGroupIDY.getRegister();
     case 2:
       assert(hasWorkGroupIDZ());
       return ArgInfo.WorkGroupIDZ.getRegister();
     }
     llvm_unreachable("unexpected dimension");
   }
 
-  /// \returns VGPR used for \p Dim' work item ID.
-  unsigned getWorkItemIDVGPR(unsigned Dim) const;
-
   unsigned getLDSWaveSpillSize() const {
     return LDSWaveSpillSize;
   }
 
   const AMDGPUBufferPseudoSourceValue *getBufferPSV(const SIInstrInfo &TII,
                                                     const Value *BufferRsrc) {
     assert(BufferRsrc);
     auto PSV = BufferPSVs.try_emplace(

lib/Target/AMDGPU/SIMachineFunctionInfo.cpp

for (auto &R : SGPRToVGPRSpills)
     MFI.RemoveStackObject(R.first);
   // All other SPGRs must be allocated on the default stack, so reset
   // the stack ID.
   for (unsigned i = MFI.getObjectIndexBegin(), e = MFI.getObjectIndexEnd();
        i != e; ++i)
     MFI.setStackID(i, 0);
 }
 
-
-/// \returns VGPR used for \p Dim' work item ID.
-unsigned SIMachineFunctionInfo::getWorkItemIDVGPR(unsigned Dim) const {
-  switch (Dim) {
-  case 0:
-    assert(hasWorkItemIDX());
-    return AMDGPU::VGPR0;
-  case 1:
-    assert(hasWorkItemIDY());
-    return AMDGPU::VGPR1;
-  case 2:
-    assert(hasWorkItemIDZ());
-    return AMDGPU::VGPR2;
-  }
-  llvm_unreachable("unexpected dimension");
-}
-
 MCPhysReg SIMachineFunctionInfo::getNextUserSGPR() const {
   assert(NumSystemSGPRs == 0 && "System SGPRs must be added after user SGPRs");
   return AMDGPU::SGPR0 + NumUserSGPRs;
 }
 
 MCPhysReg SIMachineFunctionInfo::getNextSystemSGPR() const {
   return AMDGPU::SGPR0 + NumUserSGPRs + NumSystemSGPRs;
 }