[WebAssembly] Print DEBUG_VALUE once for target indices

[aheejin]

Summary

DEBUG_VALUE comments are printed before an instruction, so they are
not printed with AddComment method as other comments are, but printed
using emitRawComment method. But currently emitDebugValueComment
calls emitRawComment twice for target-index-based DBG_VALUEs: once
in the switch-case,
https://github.com/llvm/llvm-project/blob/d77ae7f2513504655e555cd326208598093d66e2/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp#L1192-L1193
and again at the end of the method:
https://github.com/llvm/llvm-project/blob/d77ae7f2513504655e555cd326208598093d66e2/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp#L1227-L1228

This makes them printed twice. I think this happened through multiple
commits modifying and refactoring this method.

[dschuff]

LGTM. TBH i'm fine with this not having a test, since it only affects our LLVM development experience and not the output. but it's good as-is too.

[aheejin]

Delete the test

[thakis]

Could this have caused http://45.33.8.238/macm1/50579/step_11.txt ?

[aheejin]

I don't see why that can be related to this CL? This CL only affects wasm assembly printing, and only comment. Target indices are used only by wasm. remove-undef-fragment.ll doesn't even seem to go as far to print assembly, because it has -stop-after=finalize-isel.

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

case MachineOperand::MO_Immediate: {
       break;
     }
     case MachineOperand::MO_CImmediate: {
       Op.getCImm()->getValue().print(OS, false /*isSigned*/);
       break;
     }
     case MachineOperand::MO_TargetIndex: {
       OS << "!target-index(" << Op.getIndex() << "," << Op.getOffset() << ")";
-      // NOTE: Want this comment at start of line, don't emit with AddComment.
-      AP.OutStreamer->emitRawComment(OS.str());
       break;
     }
     case MachineOperand::MO_Register:
     case MachineOperand::MO_FrameIndex: {
       Register Reg;
       std::optional<StackOffset> Offset;
       if (Op.isReg()) {
         Reg = Op.getReg();