[llvm] [CodeGen] Add TRI::regunits() iterating over all register units (NFC) (PR #167901)

[Matt Arsenault via llvm-commits]

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@@ -1291,8 +1291,7 @@ bool RegAllocFastImpl::setPhysReg(MachineInstr &MI, MachineOperand &MO,
 #ifndef NDEBUG
 
 void RegAllocFastImpl::dumpState() const {
-  for (unsigned Unit = 1, UnitE = TRI->getNumRegUnits(); Unit != UnitE;
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arsenm wrote:

You could also probably just apply this in regunits(). There's probably no reason to visit the invalid case 

https://github.com/llvm/llvm-project/pull/167901