AMDGPU: Don't spill SP reg like a normal CSR

llvm-svn: 313217
diff --git a/llvm/lib/Target/AMDGPU/SIFrameLowering.h b/llvm/lib/Target/AMDGPU/SIFrameLowering.h
index c23969d..cc1c85f 100644
--- a/llvm/lib/Target/AMDGPU/SIFrameLowering.h
+++ b/llvm/lib/Target/AMDGPU/SIFrameLowering.h
@@ -35,6 +35,9 @@
   int getFrameIndexReference(const MachineFunction &MF, int FI,
                              unsigned &FrameReg) const override;
 
+  void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
+                            RegScavenger *RS = nullptr) const override;
+
   void processFunctionBeforeFrameFinalized(
     MachineFunction &MF,
     RegScavenger *RS = nullptr) const override;