apply code review suggestions

Author: VyacheslavLevytskyy

llvm/lib/Target/SPIRV/SPIRVSubtarget.cpp

@@ -158,7 +158,7 @@ void SPIRVSubtarget::initAvailableExtInstSets() {
 
 // Set available extensions after SPIRVSubtarget is created.
 void SPIRVSubtarget::initAvailableExtensions(
-    std::set<SPIRV::Extension::Extension> AllowedExtIds) {
+    const std::set<SPIRV::Extension::Extension> &AllowedExtIds) {
   AvailableExtensions.clear();
   AvailableExtensions.insert(AllowedExtIds.begin(), AllowedExtIds.end());
 

llvm/lib/Target/SPIRV/SPIRVSubtarget.h

@@ -59,7 +59,6 @@ class SPIRVSubtarget : public SPIRVGenSubtargetInfo {
 
   // TODO: Initialise the available extensions, extended instruction sets
   // based on the environment settings.
-  void initAvailableExtensions();
   void initAvailableExtInstSets();
   void accountForAMDShaderTrinaryMinmax();
 
@@ -70,8 +69,8 @@ class SPIRVSubtarget : public SPIRVGenSubtargetInfo {
                  const std::string &FS, const SPIRVTargetMachine &TM);
   SPIRVSubtarget &initSubtargetDependencies(StringRef CPU, StringRef FS);
 
-  void
-  initAvailableExtensions(std::set<SPIRV::Extension::Extension> AllowedExtIds);
+  void initAvailableExtensions(
+      const std::set<SPIRV::Extension::Extension> &AllowedExtIds);
 
   // Parses features string setting specified subtarget options.
   // The definition of this function is auto generated by tblgen.