[llvm] [M68k] Implement `CLR` instruction encoding and logic (PR #216636)

[via llvm-commits]

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@@ -333,6 +335,16 @@ void M68kInstrInfo::AddZExt(MachineBasicBlock &MBB,
                             MachineBasicBlock::iterator I, DebugLoc DL,
                             unsigned Reg, MVT From, MVT To) const {
 
+  // On 68000, SWAP -> CLR -> SWAP is faster than AND with mask.
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knickish wrote:

Where do 68010/68008 fall? 

https://github.com/llvm/llvm-project/pull/216636