[WebAssembly] Minor cleanup to WebAssemblySubtarget. NFC.

[sbc100]

Summary

Pretty much all other platforms pass CPU string as arg0 of
initializeSubtargetDependencies.

llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

class WebAssemblySubtarget final : public WebAssemblyGenSubtargetInfo {
   bool HasSignExt = false;
   bool HasExceptionHandling = false;
   bool HasBulkMemory = false;
   bool HasMultivalue = false;
   bool HasMutableGlobals = false;
   bool HasTailCall = false;
   bool HasReferenceTypes = false;
 
-  /// String name of used CPU.
-  std::string CPUString;
-
   /// What processor and OS we're targeting.
   Triple TargetTriple;
 
   WebAssemblyFrameLowering FrameLowering;
   WebAssemblyInstrInfo InstrInfo;
   WebAssemblySelectionDAGInfo TSInfo;
   WebAssemblyTargetLowering TLInfo;
 
-  /// Initializes using CPUString and the passed in feature string so that we
-  /// can use initializer lists for subtarget initialization.
-  WebAssemblySubtarget &initializeSubtargetDependencies(StringRef FS);
+  WebAssemblySubtarget &initializeSubtargetDependencies(StringRef CPU,
+                                                        StringRef FS);
 
 public:
   /// This constructor initializes the data members to match that
   /// of the specified triple.
   WebAssemblySubtarget(const Triple &TT, const std::string &CPU,
                        const std::string &FS, const TargetMachine &TM);
 
   const WebAssemblySelectionDAGInfo *getSelectionDAGInfo() const override {

llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp

 
 #define DEBUG_TYPE "wasm-subtarget"
 
 #define GET_SUBTARGETINFO_CTOR
 #define GET_SUBTARGETINFO_TARGET_DESC
 #include "WebAssemblyGenSubtargetInfo.inc"
 
 WebAssemblySubtarget &
-WebAssemblySubtarget::initializeSubtargetDependencies(StringRef FS) {
+WebAssemblySubtarget::initializeSubtargetDependencies(StringRef CPU,
+                                                      StringRef FS) {
   // Determine default and user-specified characteristics
+  LLVM_DEBUG(llvm::dbgs() << "initializeSubtargetDependencies\n");
 
-  if (CPUString.empty())
-    CPUString = "generic";
+  if (CPU.empty())
+    CPU = "generic";
 
-  ParseSubtargetFeatures(CPUString, FS);
+  ParseSubtargetFeatures(CPU, FS);
   return *this;
 }
 
 WebAssemblySubtarget::WebAssemblySubtarget(const Triple &TT,
                                            const std::string &CPU,
                                            const std::string &FS,
                                            const TargetMachine &TM)
-    : WebAssemblyGenSubtargetInfo(TT, CPU, FS), CPUString(CPU),
-      TargetTriple(TT), FrameLowering(),
-      InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
-      TLInfo(TM, *this) {}
+    : WebAssemblyGenSubtargetInfo(TT, CPU, FS), TargetTriple(TT),
+      FrameLowering(), InstrInfo(initializeSubtargetDependencies(CPU, FS)),
+      TSInfo(), TLInfo(TM, *this) {}
 
 bool WebAssemblySubtarget::enableAtomicExpand() const {
   // If atomics are disabled, atomic ops are lowered instead of expanded
   return hasAtomics();
 }
 
 bool WebAssemblySubtarget::enableMachineScheduler() const {
   // Disable the MachineScheduler for now. Even with ShouldTrackPressure set and
   // enableMachineSchedDefaultSched overridden, it appears to have an overall
   // negative effect for the kinds of register optimizations we're doing.
   return false;
 }
 
 bool WebAssemblySubtarget::useAA() const { return true; }