[XCOFF] Fix UB 'left shift of negative value' after #72532

Author: vitalybuka

llvm/lib/Target/PowerPC/MCTargetDesc/PPCInstPrinter.cpp

@@ -484,7 +484,7 @@ void PPCInstPrinter::printAbsBranchOperand(const MCInst *MI, unsigned OpNo,
   if (!MI->getOperand(OpNo).isImm())
     return printOperand(MI, OpNo, STI, O);
 
-  uint64_t Imm = MI->getOperand(OpNo).getImm() << 2;
+  uint64_t Imm = static_cast<uint64_t>(MI->getOperand(OpNo).getImm()) << 2;
   if (!TT.isPPC64())
     Imm = static_cast<uint32_t>(Imm);
   O << formatHex(Imm);