Delete unneeded X86RegisterInfo::hasReservedSpillSlot. NFC

Only PowerPC and RISCV need to override it.

llvm/lib/Target/X86/X86RegisterInfo.cpp

@@ -665,13 +665,6 @@ bool X86RegisterInfo::canRealignStack(const MachineFunction &MF) const {
   return true;
 }
 
-bool X86RegisterInfo::hasReservedSpillSlot(const MachineFunction &MF,
-                                           Register Reg, int &FrameIdx) const {
-  // Since X86 defines assignCalleeSavedSpillSlots which always return true
-  // this function neither used nor tested.
-  llvm_unreachable("Unused function on X86. Otherwise need a test case.");
-}
-
 // tryOptimizeLEAtoMOV - helper function that tries to replace a LEA instruction
 // of the form 'lea (%esp), %ebx' --> 'mov %esp, %ebx'.
 // TODO: In this case we should be really trying first to entirely eliminate

llvm/lib/Target/X86/X86RegisterInfo.h

@@ -121,9 +121,6 @@ public:
 
   bool canRealignStack(const MachineFunction &MF) const override;
 
-  bool hasReservedSpillSlot(const MachineFunction &MF, Register Reg,
-                            int &FrameIdx) const override;
-
   void eliminateFrameIndex(MachineBasicBlock::iterator MI,
                            int SPAdj, unsigned FIOperandNum,
                            RegScavenger *RS = nullptr) const override;