PPC: Fix missing const on TargetInstrInfo's subtarget reference (#157201)

Author: arsenm

llvm/lib/Target/PowerPC/PPCInstrInfo.cpp

@@ -88,7 +88,7 @@ static cl::opt<bool> EnableFMARegPressureReduction(
 // Pin the vtable to this file.
 void PPCInstrInfo::anchor() {}
 
-PPCInstrInfo::PPCInstrInfo(PPCSubtarget &STI)
+PPCInstrInfo::PPCInstrInfo(const PPCSubtarget &STI)
     : PPCGenInstrInfo(PPC::ADJCALLSTACKDOWN, PPC::ADJCALLSTACKUP,
                       /* CatchRetOpcode */ -1,
                       STI.isPPC64() ? PPC::BLR8 : PPC::BLR),

llvm/lib/Target/PowerPC/PPCInstrInfo.h

@@ -279,7 +279,7 @@ enum PPCMachineCombinerPattern : unsigned {
 
 class PPCSubtarget;
 class PPCInstrInfo : public PPCGenInstrInfo {
-  PPCSubtarget &Subtarget;
+  const PPCSubtarget &Subtarget;
   const PPCRegisterInfo RI;
   const unsigned StoreSpillOpcodesArray[4][SOK_LastOpcodeSpill] =
       StoreOpcodesForSpill;
@@ -369,7 +369,7 @@ class PPCInstrInfo : public PPCGenInstrInfo {
                                        unsigned OpIdx2) const override;
 
 public:
-  explicit PPCInstrInfo(PPCSubtarget &STI);
+  explicit PPCInstrInfo(const PPCSubtarget &STI);
 
   bool isLoadFromConstantPool(MachineInstr *I) const;
   const Constant *getConstantFromConstantPool(MachineInstr *I) const;