Merge commit '9f3afa3b1f7d' from apple/master into swift/master-next

Author: git apple-llvm automerger

llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp

@@ -189,6 +189,9 @@ void RISCVMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
   // Get byte count of instruction.
   unsigned Size = Desc.getSize();
 
+  // RISCVInstrInfo::getInstSizeInBytes hard-codes the number of expanded
+  // instructions for each pseudo, and must be updated when adding new pseudos
+  // or changing existing ones.
   if (MI.getOpcode() == RISCV::PseudoCALLReg ||
       MI.getOpcode() == RISCV::PseudoCALL ||
       MI.getOpcode() == RISCV::PseudoTAIL ||