LLVM Essentials

Printing an instruction

Printing an assembly instruction is an important step in generating target code. Various classes are defined that work as a gateway to the streamers.

First, we initialize the class for instruction, assigning the operands, the assembly string, pattern, the output variable, and so on in the TOYInstrFormats.td file:

class InstTOY<dag outs, dag ins, string asmstr, list<dag> pattern>
    : Instruction {
  field bits<32> Inst;
  let Namespace = "TOY";
  dag OutOperandList = outs;
  dag InOperandList = ins;
  let AsmString = asmstr;
  let Pattern = pattern;
  let Size = 4;
}

Then, we define functions to print operands in TOYInstPrinter.cpp.

void TOYInstPrinter::printOperand(const MCInst *MI, unsigned OpNo, raw_ostream &O) { const MCOperand &Op = MI->getOperand(OpNo); ...