[LLVMdev] MCInstPrinter::printRegName

Akira Hatanaka ahatanak at gmail.com
Wed Jul 6 11:18:14 PDT 2011

I have a question regarding implementation of subclasses of MCInstPrinter.
I am implementing Machine IR layer to MC layer lowering for Mips.

What's the best way to print the value of "Register" in the following code
in MCAsmStreamer::EmitRegisterName? Do I have to convert the LLVM register
number back to its corresponding dwarf register number in function
InstPrinter->printRegName? I just want to have it output the same register
number as before (the same output the false path would produce).

void MCAsmStreamer::EmitRegisterName(int64_t Register) {
  if (InstPrinter) {
    const TargetAsmInfo &asmInfo = getContext().getTargetAsmInfo();
    unsigned LLVMRegister = asmInfo.getLLVMRegNum(Register, true);
    InstPrinter->printRegName(OS, LLVMRegister);
  } else {
    OS << Register;

My current implementation of printRegName which I copied from other backends
(X86, ARM and PowerPC) looks like this:

void MipsInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {
  OS << getRegisterName(RegNo);

This will result in code like this
.cfi_offset RA, -4
, instead of something like this:
.cfi_offset 31, -4
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