[AArch64][AMDGPU][WebAssembly] Use static_cast instead of a reinterpret_cast to downcast in parseMachineFunctionInfo.

[craig.topper]

Summary

static_cast is a little safer here since the compiler will
ensure we're casting to a class derived from
yaml::MachineFunctionInfo.

I believe this first appeared on AMDGPU and was copied to the
other two targets.

Spotted when it was being copied to RISCV in D123178.

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

 AArch64TargetMachine::convertFuncInfoToYAML(const MachineFunction &MF) const {
   const auto *MFI = MF.getInfo<AArch64FunctionInfo>();
   return new yaml::AArch64FunctionInfo(*MFI);
 }
 
 bool AArch64TargetMachine::parseMachineFunctionInfo(
     const yaml::MachineFunctionInfo &MFI, PerFunctionMIParsingState &PFS,
     SMDiagnostic &Error, SMRange &SourceRange) const {
-  const auto &YamlMFI =
-      reinterpret_cast<const yaml::AArch64FunctionInfo &>(MFI);
+  const auto &YamlMFI = static_cast<const yaml::AArch64FunctionInfo &>(MFI);
   MachineFunction &MF = PFS.MF;
   MF.getInfo<AArch64FunctionInfo>()->initializeBaseYamlFields(YamlMFI);
   return false;
 }

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

GCNTargetMachine::convertFuncInfoToYAML(const MachineFunction &MF) const {
   return new yaml::SIMachineFunctionInfo(
       *MFI, *MF.getSubtarget().getRegisterInfo(), MF);
 }
 
 bool GCNTargetMachine::parseMachineFunctionInfo(
     const yaml::MachineFunctionInfo &MFI_, PerFunctionMIParsingState &PFS,
     SMDiagnostic &Error, SMRange &SourceRange) const {
   const yaml::SIMachineFunctionInfo &YamlMFI =
-      reinterpret_cast<const yaml::SIMachineFunctionInfo &>(MFI_);
+      static_cast<const yaml::SIMachineFunctionInfo &>(MFI_);
   MachineFunction &MF = PFS.MF;
   SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
 
   if (MFI->initializeBaseYamlFields(YamlMFI, MF, PFS, Error, SourceRange))
     return true;
 
   if (MFI->Occupancy == 0) {
     // Fixup the subtarget dependent default value.

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

yaml::MachineFunctionInfo *WebAssemblyTargetMachine::convertFuncInfoToYAML(
     const MachineFunction &MF) const {
   const auto *MFI = MF.getInfo<WebAssemblyFunctionInfo>();
   return new yaml::WebAssemblyFunctionInfo(*MFI);
 }
 
 bool WebAssemblyTargetMachine::parseMachineFunctionInfo(
     const yaml::MachineFunctionInfo &MFI, PerFunctionMIParsingState &PFS,
     SMDiagnostic &Error, SMRange &SourceRange) const {
-  const auto &YamlMFI =
-      reinterpret_cast<const yaml::WebAssemblyFunctionInfo &>(MFI);
+  const auto &YamlMFI = static_cast<const yaml::WebAssemblyFunctionInfo &>(MFI);
   MachineFunction &MF = PFS.MF;
   MF.getInfo<WebAssemblyFunctionInfo>()->initializeBaseYamlFields(YamlMFI);
   return false;
 }