Correct TRI methods to optional<> and SmallString

Author: optimisan

llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp

@@ -3840,13 +3840,13 @@ SIRegisterInfo::getSubRegAlignmentNumBits(const TargetRegisterClass *RC,
   return 0;
 }
 
-SmallVector<std::string>
+SmallVector<SmallString<8>>
 SIRegisterInfo::getVRegFlagsOfReg(Register Reg,
                                   const MachineFunction &MF) const {
-  SmallVector<std::string> RegFlags;
+  SmallVector<SmallString<8>> RegFlags;
   const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
   if (FuncInfo->checkFlag(Reg, AMDGPU::VirtRegFlag::WWM_REG)) {
-    RegFlags.push_back("WWM_REG");
+    RegFlags.push_back(SmallString<8>("WWM_REG"));
   }
   return RegFlags;
 }

llvm/lib/Target/AMDGPU/SIRegisterInfo.h

@@ -455,14 +455,14 @@ class SIRegisterInfo final : public AMDGPUGenRegisterInfo {
   unsigned getSubRegAlignmentNumBits(const TargetRegisterClass *RC,
                                      unsigned SubReg) const;
 
-  std::pair<bool, uint8_t> getVRegFlagValue(StringRef Name) const override {
+  std::optional<uint8_t> getVRegFlagValue(StringRef Name) const override {
     if (Name == "WWM_REG") {
-      return {true, AMDGPU::VirtRegFlag::WWM_REG};
+      return AMDGPU::VirtRegFlag::WWM_REG;
     }
-    return {false, 0};
+    return {};
   }
 
-  SmallVector<std::string>
+  SmallVector<SmallString<8>>
   getVRegFlagsOfReg(Register Reg, const MachineFunction &MF) const override;
 };