PPC: Use StringRef for subtarget constructor arguments (#157409)

Author: arsenm

llvm/lib/Target/PowerPC/PPCSubtarget.cpp

@@ -52,9 +52,8 @@ PPCSubtarget &PPCSubtarget::initializeSubtargetDependencies(StringRef CPU,
   return *this;
 }
 
-PPCSubtarget::PPCSubtarget(const Triple &TT, const std::string &CPU,
-                           const std::string &TuneCPU, const std::string &FS,
-                           const PPCTargetMachine &TM)
+PPCSubtarget::PPCSubtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU,
+                           StringRef FS, const PPCTargetMachine &TM)
     : PPCGenSubtargetInfo(TT, CPU, TuneCPU, FS),
       IsPPC64(getTargetTriple().getArch() == Triple::ppc64 ||
               getTargetTriple().getArch() == Triple::ppc64le),

llvm/lib/Target/PowerPC/PPCSubtarget.h

@@ -116,8 +116,7 @@ class PPCSubtarget : public PPCGenSubtargetInfo {
   /// This constructor initializes the data members to match that
   /// of the specified triple.
   ///
-  PPCSubtarget(const Triple &TT, const std::string &CPU,
-               const std::string &TuneCPU, const std::string &FS,
+  PPCSubtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU, StringRef FS,
                const PPCTargetMachine &TM);
 
   ~PPCSubtarget() override;