Add "llvm_unreachable" for function RegisterBankInfo::getRegBank

[skan]

Summary

RegClassOrBank is an object of RegClassOrRegBank, which is defined as

using llvm::RegClassOrRegBank = typedef PointerUnion<const TargetRegisterClass *, const RegisterBank *>
}

so control flow can not get here. Use ""llvm_unreachable" here to avoid "null pointer" confusion.

[skan]

add "const" to pointer type description.

[dsanders]

lib/CodeGen/GlobalISel/RegisterBankInfo.cpp

96

There's a typo here ('Reigister')

[skan]

fix the typo ("Register")

[skan]

lib/CodeGen/GlobalISel/RegisterBankInfo.cpp

96

fixed in the updated patch

[qcolombet]

llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp

96 ↗

(On Diff #201810)

Sorry for the late reply but that doesn't seem right.

Yes, RegClassOrRegBank is of one of the two classes, but it can still be nullptr, e.g., before regbankselect. Therefore this case seems reachable to me.

What am I missing?

[skan]

RegClassOrRegBank is of one of the two classes, but it can still be nullptr, e.g., before regbankselect.
This patch has been reverted in llvm trunk.

lib/CodeGen/GlobalISel/RegisterBankInfo.cpp

if (TargetRegisterInfo::isPhysicalRegister(Reg))
     return &getRegBankFromRegClass(getMinimalPhysRegClass(Reg, TRI));
 
   assert(Reg && "NoRegister does not have a register bank");
   const RegClassOrRegBank &RegClassOrBank = MRI.getRegClassOrRegBank(Reg);
   if (auto *RB = RegClassOrBank.dyn_cast<const RegisterBank *>())
     return RB;
   if (auto *RC = RegClassOrBank.dyn_cast<const TargetRegisterClass *>())
     return &getRegBankFromRegClass(*RC);
-  return nullptr;
+
+  llvm_unreachable("RegClassOrBank is either a const RegisterBank* or "
+                   "a const TargetReigisterClass*");
 }
 
 const TargetRegisterClass &
 RegisterBankInfo::getMinimalPhysRegClass(unsigned Reg,
                                          const TargetRegisterInfo &TRI) const {
   assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
          "Reg must be a physreg");
   const auto &RegRCIt = PhysRegMinimalRCs.find(Reg);