[MC] Remove PhysRegSize from MCRegisterClass

[bjope]

Summary

The interface to get size and spill size of a register
was moved from MCRegisterInfo to TargetRegisterInfo over
a year ago. Afaik the old interface has bee around
to give out-of-tree targets a chance to adapt to the
new interface.

One problem with the old MCRegisterClass::PhysRegSize was that
it represented the size of a register as "size in bits" / 8.
So a register had to be a multiple of eight bits wide for the
size to be correct (and the byte size for the target needed to
be eight bits).

[bjope]

Is this cleanup OK now?
I know that @kparzysz tried this originally in https://reviews.llvm.org/D31299, but that refactoring ended up leaving these methods and the PhysRegSize member around.

It looks like @qcolombet had some opinions about this last time. The original solution for D31299 was reverted in r298727 with the message being "Revert r298652 on Quentin's request.
I'm not sure what the problem was. Is this code actually used from somewhere, or was it just to give out-of-tree clones some time to adapt to the new interface?

[kparzysz]

I'm ok with it, but please wait for Quentin's input.

[kparzysz]

Accepting as per comments in D50285.

[bjope]

In D47199#1192530, @kparzysz wrote:

Accepting as per comments in D50285.

Thanks! I've landed this now.
If it is reverted we can try with D50285 instead. But I really hope this should be OK. We have had it like this in our OOT repo for a long time. We needed to detect if someone starts using getSize()/getPhysRegSize(), as those methods simply doesn't make sense for some of our non-byte sized registers.

include/llvm/MC/MCRegisterInfo.h

public:
   using const_iterator = const MCPhysReg*;
 
   const iterator RegsBegin;
   const uint8_t *const RegSet;
   const uint32_t NameIdx;
   const uint16_t RegsSize;
   const uint16_t RegSetSize;
   const uint16_t ID;
-  const uint16_t PhysRegSize;
   const int8_t CopyCost;
   const bool Allocatable;
 
   /// getID() - Return the register class ID number.
   ///
   unsigned getID() const { return ID; }
 
   /// begin/end - Return all of the registers in this class.
bool contains(unsigned Reg) const {
     return (RegSet[Byte] & (1 << InByte)) != 0;
   }
 
   /// contains - Return true if both registers are in this class.
   bool contains(unsigned Reg1, unsigned Reg2) const {
     return contains(Reg1) && contains(Reg2);
   }
 
-  /// Return the size of the physical register in bytes.
-  unsigned getPhysRegSize() const { return PhysRegSize; }
-  /// Temporary function to allow out-of-tree targets to switch.
-  unsigned getSize() const { return getPhysRegSize(); }
-
   /// getCopyCost - Return the cost of copying a value between two registers in
   /// this class. A negative number means the register class is very expensive
   /// to copy e.g. status flag register classes.
   int getCopyCost() const { return CopyCost; }
 
   /// isAllocatable - Return true if this register class may be used to create
   /// virtual registers.
   bool isAllocatable() const { return Allocatable; }

lib/CodeGen/TargetInstrInfo.cpp

bool TargetInstrInfo::getStackSlotRange(const TargetRegisterClass *RC,
                                         const MachineFunction &MF) const {
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
   if (!SubIdx) {
     Size = TRI->getSpillSize(*RC);
     Offset = 0;
     return true;
   }
   unsigned BitSize = TRI->getSubRegIdxSize(SubIdx);
-  // Convert bit size to byte size to be consistent with
-  // MCRegisterClass::getSize().
+  // Convert bit size to byte size.
   if (BitSize % 8)
     return false;
 
   int BitOffset = TRI->getSubRegIdxOffset(SubIdx);
   if (BitOffset < 0 || BitOffset % 8)
     return false;
 
   Size = BitSize /= 8;

utils/TableGen/RegisterInfoEmitter.cpp

#endif
   RegClassStrings.emit(OS, printChar);
   OS << "};\n\n";
 
   OS << "extern const MCRegisterClass " << TargetName
      << "MCRegisterClasses[] = {\n";
 
   for (const auto &RC : RegisterClasses) {
     assert(isInt<8>(RC.CopyCost) && "Copy cost too large.");
-    uint32_t RegSize = 0;
-    if (RC.RSI.isSimple())
-      RegSize = RC.RSI.getSimple().RegSize;
     OS << "  { " << RC.getName() << ", " << RC.getName() << "Bits, "
        << RegClassStrings.get(RC.getName()) << ", "
        << RC.getOrder().size() << ", sizeof(" << RC.getName() << "Bits), "
        << RC.getQualifiedName() + "RegClassID" << ", "
-       << RegSize/8 << ", "
        << RC.CopyCost << ", "
        << ( RC.Allocatable ? "true" : "false" ) << " },\n";
   }
 
   OS << "};\n\n";
 
   EmitRegMappingTables(OS, Regs, false);